CN106531782A - Metal oxide thin film transistor and manufacturing method thereof - Google Patents

Abstract

The present invention provides a metal oxide thin film transistor and a preparation method thereof. The metal oxide thin film transistor includes a substrate, a gate, a gate insulating layer, a metal oxide semiconductor layer and The barrier layer, the passivation layer arranged on the outermost layer, and the source electrode and the drain electrode respectively connected to the metal oxide semiconductor layer; side; the diffusion element is any one of fluorine, nitrogen and hydrogen. The preparation method adopts the following method, the barrier layer adjacent to the insulator film layer containing the diffusion element is arranged on the side opposite to the metal oxide semiconductor layer, and the diffusion element is any one of fluorine, nitrogen and hydrogen elements; the fluorine Elements of nitrogen, nitrogen or hydrogen are diffused into the metal oxide semiconductor layer of the thin film transistor through a thermal diffusion method, until the interface between the metal oxide semiconductor thin film and the gate insulating layer.

Description

A kind of metal oxide thin film transistor and its preparation method

technical field

The invention relates to the field of preparation of metal oxide thin film transistors, in particular to a metal oxide thin film transistor and a preparation method thereof.

Background technique

As the core component of the active switching/driving of each pixel of a display device, thin film transistors have been widely used in flat panel displays such as organic electroluminescent displays and liquid crystal displays. As a bridge between people and various electronic products, flat panel displays, with the development of modern industry and the continuous improvement of people's living standards, the next generation of display technology will not only further improve the display quality, but also gradually expand to large-area, high-resolution High-speed, thin, flexible and rollable type. Traditional silicon-based thin-film transistors are no longer sufficient for next-generation display technologies. However, metal oxide semiconductor materials have excellent properties such as high electron mobility, good visible light transmittance, and can be prepared at low temperature or even room temperature. Compared with traditional silicon-based thin film transistors, metal oxide thin film transistors have the advantages of wide bandgap, high uniformity, high stability, and high field effect mobility, which is conducive to industrial production and caters to the development trend of modern display technology.

In recent years, amorphous metal oxide semiconductors have become a research hotspot in the active layer of thin film transistors, such as zinc oxide, indium oxide, indium tin zinc oxide, zinc tin oxide and gallium zinc oxide. Compared with silicon-based materials, wide-bandgap amorphous metal oxide semiconductor materials have lower defect state density. This makes metal oxide thin film transistors not only have obvious advantages in field effect mobility, light transmittance, uniformity, etc., but also have ideal characteristic curves, including low threshold voltage, low off-state current, steep subthreshold swing, negligible hysteresis and high source-to-drain current switching ratio. However, in the process of preparing thin film transistors, factors such as its structure, preparation conditions of each layer of thin film, photolithography technology, etching method and annealing method all affect the defect type and its density of states in the metal oxide semiconductor forbidden band and the active layer The charge trap density at the interface with the insulating layer, which affects the operating characteristics and stability of the transistor.

Although the working characteristics and stability of the metal oxide thin film transistor can be improved by optimizing the experimental parameters, the thin film transistor is affected by gate bias, light, temperature, and atmosphere during operation. For a bottom-gate thin film transistor without a barrier layer and a passivation layer, if the back channel surface of the active layer is exposed to the air, the stability of the thin film transistor is easily affected by the field-induced absorption/desorption effect of oxygen and water vapor in the air. In recent years, researchers at home and abroad have used various insulator materials as passivation layers, such as silicon oxide, silicon nitride, titanium oxide, and aluminum oxide. The stability of thin film transistors in the actual working environment is a key issue that determines whether they can be applied to flat panel displays and realize industrial development. When switching/driving liquid crystal displays and organic electroluminescent displays, thin film transistors often work at negative gate bias and are exposed to backlight or natural light, and at the same time, thin film transistors are affected by the thermal effect of the substrate, especially under negative bias lighting stress and positive Under bias temperature stress conditions, it will cause threshold voltage drift. It has been reported that the threshold shift is attributed to the charge binding in the gate insulating layer, the interface between the active layer and the insulating layer, the interface between the active layer, the barrier layer and the active layer, and the deep main type defects generated, which are the causes of thin film A key factor in the deterioration of transistor stability.

Looking at the research work of various panel manufacturers and scientific research institutions, in order to fundamentally solve the problem of the stability of metal oxide thin film transistors, researchers mainly focus on the following two aspects: one is to reduce oxygen vacancies in oxide semiconductors through oxidation Defect state density, the main method is to anneal the thin film transistor in an oxygen-rich atmosphere, such as oxygen annealing treatment, oxygen plasma treatment and the like. On the other hand, it is to deactivate the defects existing in the oxide semiconductor, such as introducing new elements to form stable chemical bonds with the defects in the semiconductor, such as hydrogen annealing treatment, hydrogen plasma treatment, etc. Existing technical methods require relatively harsh experimental conditions in the implementation process. Some require high temperature and high pressure, very expensive equipment or complex processes, poor uniformity, and poor repeatability. It is difficult to achieve simple processes, low cost, and large areas. Industrialized production of high-stability thin film transistors.

Contents of the invention

Aiming at the problems existing in the prior art, the present invention provides a metal oxide thin film transistor and a preparation method thereof, which has the advantages of simple process, good uniformity, large area, good repeatability and high stability.

The present invention is achieved through the following technical solutions:

A metal oxide thin film transistor, comprising a substrate, a gate, a gate insulating layer, a metal oxide semiconductor layer and a barrier layer arranged in layers on the substrate, a passivation layer arranged on the outermost layer, and The source electrode and the drain electrode connected by the metal oxide semiconductor layer; the barrier layer adjacent to the insulator film layer containing the diffusion element is arranged on the side opposite to the metal oxide semiconductor layer; the diffusion element is fluorine, nitrogen and hydrogen elements any kind.

Preferably, the source electrode and the drain electrode are arranged in the passivation layer, and the lower ends are respectively connected to the metal oxide semiconductor layer through the insulator film layer containing diffusion elements and the barrier layer; the metal oxide semiconductor layer is wrapped between the gate insulating layer and the barrier layer between.

Preferably, the barrier layer and the insulator thin film layer containing diffusion elements are wrapped between the metal oxide semiconductor layer and the passivation layer; the source electrode and the drain electrode are arranged on the passivation layer, and the lower end passes through the passivation layer and is connected with the metal oxide semiconductor layer respectively. layer connections.

A method for preparing a metal oxide thin film transistor, wherein the metal oxide thin film transistor includes a layer of an insulator film layer containing a diffusion element; the barrier layer adjacent to the insulator film layer containing a diffusion element is arranged on the opposite side of the metal oxide semiconductor layer On the one hand, the diffusion element is any one of fluorine, nitrogen and hydrogen elements; the fluorine, nitrogen or hydrogen elements are diffused into the metal oxide semiconductor layer of the thin film transistor by a thermal diffusion method until the metal oxide semiconductor at the interface between the thin film and the gate insulating layer.

Preferably, the thermal diffusion method is to heat-treat the thin film transistor by means of rapid annealing, the annealing temperature is 250-350° C., and the annealing time is 30-180 minutes.

Preferably, the insulator film layer containing diffusion elements is any one of a fluorine-doped silicon oxide film layer, a fluorine-doped silicon nitride film layer, a nitrogen-doped silicon oxide film layer, a hydrogen-doped silicon oxide film layer and a hydrogen-doped silicon nitride film layer kind.

Preferably, the insulator film layer containing diffusion elements is prepared by any one of magnetron sputtering, spin coating, vacuum evaporation, atomic layer deposition and non-vacuum chemical deposition methods; its thickness is controlled at 10- 100nm.

Preferably, the thickness of the barrier layer is controlled at 50-150 nm.

Preferably, the structure of the metal oxide thin film transistor is any one of bottom-gate-bottom-contact, bottom-gate-top-contact, top-by-bottom contact and top-by-top contact.

Preferably, the prepared metal oxide thin film transistor has a field effect mobility greater than 12cm ² V ^-1 s ^-1 , a turn-on voltage less than 0.5V, a subthreshold swing less than 0.2, and negligible hysteresis. The threshold voltage shift was less than 0.1V under the bias stress of 10 ⁴ s, and the threshold voltage shift was less than 0.2V under the -20V negative bias of 460nm light stress for 10 ⁴ s.

Compared with the prior art, the present invention has the following beneficial technical effects:

The method for preparing the metal oxide thin film transistor of the present invention effectively improves the stability of the thin film transistor through thermal diffusion while improving the quality of the oxide semiconductor layer in a heat treatment environment at 250-350°C. A layer of insulator film containing fluorine, nitrogen or hydrogen is deposited between the barrier layer and the passivation layer of the thin film transistor through a simple preparation method, which not only avoids the influence of the external environment on this film layer, but also realizes the presence of certain elements in the film. Uniform diffusion in the metal oxide semiconductor layer, thereby improving the stability of the thin film transistor. The metal oxide thin film transistor realized by the inventive method has the characteristics of simple process, good uniformity, large area, good repeatability and high stability.

Furthermore, this method is compatible with the existing flat panel display process technology, is suitable for industrial production, and improves production efficiency.

Furthermore, the thermal diffusion treatment can be realized for different metal oxide semiconductor layers in the thin film transistor, and the application range is wide, and an ideal high-stability metal oxide thin film transistor can be obtained.

Further, after the thermal diffusion treatment, the thin film transistor can be transferred to a flexible substrate by a printing method to realize a flexible rollable device.

In the metal oxide thin film transistor of the present invention, the stability of the insulator thin film layer containing diffusion elements arranged on the side opposite to the metal oxide semiconductor layer adjacent to the barrier layer is improved; its structure and working principle are as follows. (1) The above-mentioned diffusion elements can fill the oxygen vacancies in metal oxide semiconductors to reduce the defect state density of metal oxide semiconductors, and realize the light stability of thin-film transistors; (2) The above-mentioned diffusion elements replace oxygen in weak metal oxygen ion bonds to realize thin-film Transistor structural stability; (3) the above-mentioned diffused elements form strong metal-element ionic bonds with metals, since the metal-element ionic bond energy is greater than the metal oxygen ion bond energy, the thermal stability of thin film transistors can be achieved; (4) the above-mentioned diffusion Elements serve as shallow donor energy levels to increase carrier concentration and realize low-resistivity metal oxide semiconductor films; (5) the above-mentioned diffusion elements can replace silicon-hydrogen bonds and silicon-hydroxyl bonds to form stable silicon-element bonds, effectively reducing the metal oxide semiconductor The density of traps at the interface between the thin film and the insulating layer.

Description of drawings

FIG. 1 is a schematic structural view of the metal oxide thin film transistor described in Example 1-3 of the present invention.

FIG. 2 is a schematic structural view of the metal oxide thin film transistor described in Example 4-5 of the present invention.

FIG. 3 is a schematic structural diagram of the metal oxide thin film transistor described in Example 6 of the present invention.

FIG. 4 is a schematic structural diagram of the metal oxide thin film transistor described in Example 7 of the present invention.

FIG. 5 is a schematic structural diagram of the metal oxide thin film transistor described in Example 8 of the present invention.

In the figure: 1 is the substrate, 2 is the gate, 3 is the gate insulating layer, 4 is the metal oxide semiconductor layer, 5 is the barrier layer, 6 is the insulator film layer containing diffusion elements, 7 is the source, 8 is the drain , 9 is the passivation layer.

detailed description

The present invention will be further described in detail below in conjunction with specific embodiments, which are explanations of the present invention rather than limitations.

Example 1

A method for preparing a metal oxide thin film transistor, comprising the steps of:

1) Preparation of the metal oxide semiconductor thin film: after preparing the gate 2 and the gate insulating layer 3 based on the structure in Fig. 1, when the metal oxide semiconductor layer 4 is prepared by magnetron sputtering, the target material is indium gallium zinc oxide as an example , the deposition gas atmosphere is nitrogen and oxygen, the ratio is 29.4:0.6sccm, the deposition temperature is 150°C, the deposition power is 180W, the deposition pressure is 1Pa, and the deposition thickness is 50nm.

2) Prepare a barrier layer 5 after referring to FIG. 1 with a thickness of 100 nm.

3) Preparation of fluorine-doped silicon nitride thin film layer 6: After step 2), fluorine-doped silicon nitride is prepared by plasma-enhanced chemical vapor deposition, and the deposition gas atmosphere is silicon tetrafluoride, nitrous oxide, and nitrogen. The flow rates were 2, 100, and 120 sccm, the deposition pressure was 110 Pa, the deposition power was 50 W, the deposition temperature was 170° C., and the deposition thickness was 50 nm.

4) After step 3), the source electrode 7, the drain electrode 8, and the passivation layer 9 are sequentially prepared.

5) The thin film transistor is heat-treated by rapid annealing method, the annealing temperature is 350° C., the annealing time is 1 hour, and the annealing atmosphere is nitrogen.

6) The field effect mobility of the fluorine-doped oxide thin film transistor is 12cm ² V ^-1 s ^-1 , the turn-on voltage is 0.5V, and the subthreshold swing is less than 0.2.

7) The threshold voltage shift is less than 0.1V under the condition of 20V positive bias stress for 10 ⁴ s, and the threshold voltage shift is less than 0.2V under the condition of -20V negative bias (460nm) light stress for 10 ⁴ s. Its light stability is comparable to that of existing commercial polysilicon thin film transistors.

Example 2

A method for preparing a metal oxide thin film transistor, comprising the steps of:

1) Preparation of the metal oxide semiconductor thin film: after preparing the gate 2 and the gate insulating layer 3 based on the structure in FIG. Zinc fluoride and indium acetate, the solvents are water and methanol, 10 and 90 mL respectively, stirred at room temperature for 3 hours, and then filtered through a 0.2 μm filter. The deposition conditions are as follows, the deposition gas is air, the deposition temperature is 350° C., and the deposition thickness is 45 nm.

2) After referring to FIG. 1 , a barrier layer 5 is prepared with a thickness of 50 nm.

3) Preparation of nitrogen-doped silicon oxide thin film layer 6: After step 2), nitrogen-doped silicon oxide is prepared by magnetron sputtering, the target material is silicon oxide, and the deposition gas atmosphere is nitrogen, oxygen, nitrogen, and the ratio is 27.4 :0.6:2.0sccm, the deposition temperature is 150°C, the deposition power is 180W, the deposition pressure is 1Pa, and the deposition thickness is 10nm.

4) After step 3), the source electrode 7, the drain electrode 8, and the passivation layer 9 are sequentially prepared.

5) Heat-treating the thin film transistor by means of rapid annealing, the annealing temperature is 250° C., the annealing time is 120 minutes, and the annealing atmosphere is nitrogen.

6) The field-effect mobility of the nitrogen-doped oxide thin film transistor is 14cm ² V ^-1 s ^-1 , the turn-on voltage is 0.5V, and the subthreshold swing is less than 0.2.

7) The threshold voltage shift is less than 0.1V under the condition of 20V positive bias stress for 10 ⁴ s, and the threshold voltage shift is less than 0.2V under the condition of -20V negative bias (460nm) light stress for 10 ⁴ s. Its light stability is comparable to that of existing commercial polysilicon thin film transistors.

Example 3

A method for preparing a metal oxide thin film transistor, comprising the steps of:

1) Preparation of the metal oxide semiconductor thin film: after preparing the gate 2 and the gate insulating layer 3 based on the structure in FIG. Zinc acetate, 0.1M indium nitrate, and water as the solvent, stirred at room temperature for 3 hours, and then filtered through a 0.2 μm filter. After that, it was spin-coated at 4000rpm for 30s, and then heat-treated at 250°C for 1 hour in air atmosphere.

2) After referring to FIG. 1, a barrier layer 5 is prepared with a thickness of 150 nm.

3) Preparation of hydrogen-doped silicon nitride thin film layer 6: After step 2), hydrogen-doped silicon nitride is prepared by plasma enhanced chemical vapor deposition. The deposition gas atmosphere is silicon tetrafluoride, ammonia, nitrogen, and the flow rates are respectively The deposition pressure is 110Pa, the deposition power is 50W, the deposition temperature is 170°C, and the deposition thickness is 100nm.

4) After step 3), the source electrode 7, the drain electrode 8, and the passivation layer 9 are sequentially prepared.

5) The thin film transistor is heat-treated by rapid annealing method, the annealing temperature is 350° C., the annealing time is 3 hours, and the annealing atmosphere is nitrogen.

6) The field effect mobility of the hydrogen-doped oxide thin film transistor is 12cm ² V ^-1 s ^-1 , the turn-on voltage is 0.4V, and the subthreshold swing is less than 0.2.

7) The threshold voltage shift is less than 0.1V under the condition of 20V positive bias stress for 10 ⁴ s, and the threshold voltage shift is less than 0.2V under the condition of -20V negative bias (460nm) light stress for 10 ⁴ s. Its light stability is comparable to that of existing commercial polysilicon thin film transistors.

Example 4

A method for preparing a metal oxide thin film transistor, comprising the steps of:

1) Preparation of the metal oxide semiconductor thin film: refer to the structure of the self-aligned thin film transistor in Figure 2 to prepare the gate 2 and the gate insulating layer 3. When the metal oxide semiconductor layer 4 is prepared by the magnetron sputtering method, the target is used Take indium gallium zinc as an example, its atomic number ratio is 1:1:1, the deposition gas atmosphere is nitrogen and oxygen, the flow rates are 29.4 and 0.6 sccm respectively, the deposition temperature is 150°C, the deposition power is 180W, and the deposition pressure is 1Pa , with a deposition thickness of 50 nm.

2) Preparation of the barrier layer 5: After step 1), the barrier layer 5 was prepared by plasma enhanced chemical vapor deposition, the deposition gas atmosphere was silane, nitrous oxide, nitrogen, and the flow rates were 2, 100, 120 sccm respectively. The pressure is 110Pa, the deposition power is 50W, the deposition temperature is 170°C, and the deposition thickness is 50nm.

3) Preparation of fluorine-doped silicon nitride thin film layer 6: After step 2), fluorine-doped silicon nitride is prepared by plasma-enhanced chemical vapor deposition, and the deposition gas atmosphere is silicon tetrafluoride, nitrous oxide, and nitrogen. The flow rates were 2, 100, and 120 sccm, the deposition pressure was 110 Pa, the deposition power was 50 W, the deposition temperature was 170° C., and the deposition thickness was 50 nm.

4) After step 3), the passivation layer 9, the source electrode 7, and the drain electrode 8 are sequentially prepared.

5) The thin film transistor is heat-treated by rapid annealing method, the annealing temperature is 350° C., the annealing time is 30 minutes, and the annealing atmosphere is nitrogen.

6) The field effect mobility of the self-aligned fluorine-doped oxide thin film transistor is 15cm ² V ^-1 s ^-1 , the turn-on voltage is 0.3V, and the subthreshold swing is less than 0.2.

7) The threshold voltage shift is less than 0.1V under the condition of 20V positive bias stress for 10 ⁴ s, and the threshold voltage shift is less than 0.1V under the condition of -20V negative bias (460nm) light stress for 10 ⁴ s. Its light stability is comparable to that of existing commercial polysilicon thin film transistors.

Example 5

Step 1, sequentially preparing a gate 2, a gate insulating layer 3 and a metal oxide semiconductor layer 4 on a substrate 1;

Step 2, preparing a barrier layer 5 with a thickness of 70nm;

Step 3, preparing an insulator film layer 6 containing diffusion elements on the barrier layer 5; the diffusion elements are any one of fluorine, nitrogen and hydrogen elements;

Step 4, preparing the source electrode 7, the drain electrode 8 and the passivation layer 9 respectively.

Step 5, heat treatment, performing heat treatment on the thin film transistor by means of rapid annealing, the annealing temperature is 270° C., and the annealing time is 50 minutes.

The metal oxide thin film transistors prepared as described in Examples 1-5 above all have bottom-gate and top-contact structures.

Example 6

A method for preparing a metal oxide thin film transistor, as shown in Figure 3, taking a bottom-gate bottom-contact structure as an example, comprising the following steps,

Step 1, sequentially preparing a gate 2, a gate insulating layer 3, a source 7, a drain 8 and a metal oxide semiconductor layer 4 on a substrate 1;

Step 2, preparing a barrier layer 5 with a thickness of 90nm;

Step 3, preparing an insulator film layer 6 containing diffusion elements on the barrier layer 5; the diffusion elements are any one of fluorine, nitrogen and hydrogen elements;

Step 4, prepare passivation layer 9;

Step 5, heat treatment, performing heat treatment on the thin film transistor by means of rapid annealing, the annealing temperature is 290° C., and the annealing time is 70 minutes.

Example 7

A method for preparing a metal oxide thin film transistor, as shown in Figure 4, taking the top-deleted bottom contact structure as an example, as shown in the figure, includes the following steps,

Step 1, preparing an insulator film layer 6 containing diffusion elements on the substrate 1; the diffusion elements are any one of fluorine, nitrogen and hydrogen elements;

Step 2, preparing a barrier layer 5 with a thickness of 130nm;

Step 3, followed by sequentially preparing the source electrode 7, the drain electrode 8, the metal oxide semiconductor layer 4, the gate insulating layer 3, the gate electrode 2, and the passivation layer 9;

Step 4, heat treatment, performing heat treatment on the thin film transistor by means of rapid annealing, the annealing temperature is 310° C., and the annealing time is 90 minutes.

Example 8

A method for preparing a metal oxide thin film transistor, as shown in Figure 5, taking a top-by-top contact structure as an example, comprising the following steps,

Step 1, preparing an insulator film layer 6 containing diffusion elements on the substrate 1; the diffusion elements are any one of fluorine, nitrogen and hydrogen elements;

Step 2, preparing a barrier layer 5 with a thickness of 110 nm;

Step 3, followed by sequentially preparing the metal oxide semiconductor layer 4, the source electrode 7, the drain electrode 8, the gate insulating layer 3, the gate electrode 2, and the passivation layer 9;

Step 4, heat treatment, performing heat treatment on the thin film transistor by means of rapid annealing, the annealing temperature is 300° C., and the annealing time is 150 minutes.

The metal oxide thin film transistor device with high stability realized by the invention can be applied to the fields of active matrix organic light emitting diode displays, liquid crystal displays, and flexible and portable electronic products. It should be noted that the experimental parameters, working environment, test conditions, device size, proportion ratio, etc. involved in the examples of the present invention do not limit the preparation process of metal oxide thin film transistor devices. In the actual production process, according to specific conditions, Make adjustments accordingly. The above examples are only used to illustrate the technical scheme of the present invention rather than limiting the protection scope of the present invention. Although the present invention has been described in detail in the examples, it should be understood by those skilled in the art that the experimental scheme listed in the present invention can be carried out Modification or replacement without departing from the spirit and scope of the technical solution of the present invention.

Claims (10)

1. A metal oxide thin film transistor is characterized in that it comprises a substrate (1), a grid (2), a gate insulating layer (3) and a metal oxide semiconductor layer that are arranged on the substrate (1) in a layered manner. layer (4) and barrier layer (5), a passivation layer (9) disposed on the outermost layer, and a source electrode (7) and a drain electrode (8) respectively connected to the metal oxide semiconductor layer (4); The diffusion element insulator thin film layer (6) is arranged adjacent to the barrier layer (5) on the side opposite to the metal oxide semiconductor layer (4); the diffusion element is any one of fluorine, nitrogen and hydrogen elements. 2. A metal oxide thin film transistor according to claim 1, characterized in that the source (7) and the drain (8) are arranged in the passivation layer (9), and the lower end passes through the insulator film containing diffusion elements The layer (6) and the barrier layer (5) are respectively connected to the metal oxide semiconductor layer (4); the metal oxide semiconductor layer (4) is wrapped between the gate insulating layer (3) and the barrier layer (5). 3. A metal oxide thin film transistor according to claim 1, characterized in that the barrier layer (5) and the insulator film layer (6) containing diffusion elements are wrapped in the metal oxide semiconductor layer (4) and the passivation layer Between (9); the source (7) and the drain (8) are arranged on the passivation layer (9), and the lower ends pass through the passivation layer (9) and are respectively connected to the metal oxide semiconductor layer (4). 4. A method for preparing a metal oxide thin film transistor, characterized in that, the metal oxide thin film transistor includes a layer of insulator film layer (6) containing diffusion elements; adjacent to the insulator film layer (6) containing diffusion elements The barrier layer (5) is arranged on the side opposite to the metal oxide semiconductor layer (4), and the diffusion element is any one of fluorine, nitrogen and hydrogen elements; , diffuse into the metal oxide semiconductor layer (4) of the thin film transistor, until the interface between the metal oxide semiconductor film (4) and the gate insulating layer (3). 5. A method for preparing a metal oxide thin film transistor according to claim 4, characterized in that the thermal diffusion method is to heat-treat the thin film transistor by means of rapid annealing, the annealing temperature is 250-350°C, and the annealing time for 30-180 minutes. 6. The preparation method of a metal oxide thin film transistor according to claim 4, characterized in that the insulator film layer (6) containing diffusion elements is a fluorine-doped silicon oxide film layer, a fluorine-doped silicon nitride film layer, a nitrogen-doped Any one of silicon oxide film layer, hydrogen-doped silicon oxide film layer and hydrogen-doped silicon nitride film layer. 7. a kind of metal oxide thin film transistor preparation method according to claim 4 is characterized in that, the insulator thin film layer (6) containing diffusion element is passed magnetron sputtering method, spin coating method, vacuum evaporation method, atomic layer It is prepared by any one of deposition and non-vacuum chemical deposition methods; its thickness is controlled at 10-100nm. 8. A method for manufacturing a metal oxide thin film transistor according to claim 4, characterized in that the thickness of the barrier layer (5) is controlled at 50-150 nm. 9. A method for preparing a metal oxide thin film transistor according to claim 4, wherein the structure of the metal oxide thin film transistor is configured as bottom gate bottom contact, bottom gate top contact, top-by-bottom contact and top-by-top contact any of the types. 10. A method for preparing a metal oxide thin film transistor according to claim 4, characterized in that the prepared metal oxide thin film transistor has a field effect mobility greater than 12 cm ² V ^-1 s ^-1 and a turn-on voltage less than 0.5V, subthreshold swing less than 0.2, negligible hysteresis, threshold voltage drift less than 0.1V under 20V positive bias stress for 10 ⁴ s, under -20V negative bias 460nm light stress for 10 ⁴ s Threshold voltage drift is less than 0.2V.