A method for improving the reliability of flexible oxide TFT devices by low temperature plasma post-treatment

Abstract

The present invention discloses a method for improving the reliability of a flexible oxide TFT device by low-temperature plasma post-treatment. The preparation method comprises the following steps: (1) preparing a gate, an insulating layer and an active layer; (2) performing oxygen atmosphere annealing at a relatively low temperature; (3) performing a two-step mask plasma treatment, wherein the first step is high-energy nitrogen plasma treatment, and the second step is low-energy nitrogen + oxygen mixed gas plasma treatment; (4) preparing an aluminum source and drain electrode by direct current sputtering to obtain a TFT device. The method of the present invention has the advantages of simple equipment, large-area processing, short processing time, and low process temperature. The two-step plasma treatment method is adopted to give full play to its optimization effect of energy transfer and interface reaction. The low-temperature process will not cause damage to the flexible substrate, and it is generally applicable to improving the reliability of flexible AOS-TFT devices.

Description

Technical Field

[0001] The invention belongs to the technical field of microelectronics manufacturing, and in particular relates to a method for improving the reliability of a flexible oxide TFT device by low-temperature plasma post-treatment. Background Art

[0002] With the vigorous development of the electronic information industry, branch industries such as flat panel display, flexible electronics, and third-generation semiconductor devices have also sprung up like mushrooms after rain. Thin film transistors, as common microelectronic switching devices, are also an important component. Compared with the current mainstream TFT, amorphous metal oxide semiconductor materials (AOS) have attracted widespread attention at home and abroad due to their advantages such as high carrier mobility, low preparation temperature, good electrical uniformity, transparency to visible light, and low cost. Although the current AOS-TFT has many advantages in display, the instability of electro-optical and thermal instability during the operation of TFT is currently a major problem. Although AOS films can be prepared by a variety of methods, TFT devices using AOS as the active layer often need to be thermally annealed at a sufficiently high temperature to show the best performance. The annealing temperature of conventional oxide TFTs is generally around 350℃~400℃, which is higher than the glass transition temperature of ordinary flexible substrates (polyethylene terephthalate PET, polyethylene naphthenate PEN, and polyimide PI), which may cause irreversible damage to the flexible substrate. For flexible electronic devices, it is a necessary condition to be able to prepare devices at low temperatures. In order to protect the flexible substrate, the annealing temperature should be lower than the glass transition temperature of the flexible substrate, but the thermal repair of the internal defect state of the oxide semiconductor material is not sufficient, and the performance of the flexible TFT device may not reach the best and cannot meet the driving requirements, which leads to the current situation that the performance of flexible electronic devices generally lags behind that of rigid substrate devices. So far, there are still few reports in the literature on effective and universal post-processing processes to replace high-temperature annealing. The current mainstream low-temperature post-processing processes in academia include: pulsed laser annealing (short processing time; but the transient energy is too high, the effective area is too small, and the equipment is expensive), deep ultraviolet light (low cost, the most widely used; but the processing time is long), high-energy flash annealing (suitable for large-area processing; but the transient energy is too high, which may cause substrate damage, and the equipment is expensive), etc. The above processing methods are all carried out in a single energy transfer mode, which has more or less limitations. Summary of the invention

[0003] In order to solve the shortcomings and deficiencies of the prior art, an object of the present invention is to provide a method for improving the reliability of a flexible oxide TFT device by low temperature plasma post-treatment.

[0004] The method of the present invention can significantly improve the reliability of flexible electronic devices without high-temperature annealing.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A method for improving the reliability of a flexible oxide TFT device by low temperature plasma post-treatment comprises the following steps:

[0007] (1) depositing a metal film on a substrate as a gate, oxidizing part of the metal film into an oxide film as an insulating layer, and then using a mask patterning method to prepare an active layer;

[0008] (2) annealing the active layer of step (1) at 100 to 300° C. in an oxygen atmosphere for 1 to 3 hours;

[0009] (3) treating the back channel of the active layer after annealing in step (2) using high energy nitrogen plasma;

[0010] (4) treating the back channel of the active layer obtained in step (3) with a mixed gas plasma of low-energy nitrogen and oxygen;

[0011] (5) Using a mask patterning method to prepare source and drain electrodes on the back channel of the active layer, a TFT device is obtained.

[0012] Preferably, the substrate in step (1) is a polyimide (PI) substrate.

[0013] Preferably, the deposition in step (1) adopts pulsed DC sputtering technology, and the equipment power supply provides a sputtering working mode of DC plus reverse pulse voltage.

[0014] Preferably, the material of the metal film in step (1) is Al-Nd alloy; and the thickness of the gate is 100 to 400 nm.

[0015] Preferably, the thickness of the insulating layer in step (1) is 100 to 300 nm.

[0016] Preferably, the active layer material in step (1) is Al-Nd:InZnO, and has a thickness of 10 to 30 nm.

[0017] Preferably, the annealing treatment in step (2) is performed at a temperature of 200° C. and for a time of 1 hour.

[0018] Preferably, the conditions for the high-energy nitrogen plasma treatment in step (3) are: power 60-100 W, gas pressure 0.3-0.6 Torr, and treatment time 5-30 minutes; more preferably: power 70 W, gas pressure 0.4 Torr, and treatment time 5 minutes.

[0019] Preferably, the conditions for the low-energy nitrogen and oxygen mixed gas plasma treatment in step (4) are: a flow ratio of nitrogen to oxygen of 1:9 to 1:1, a power of 10 to 50 W, a gas pressure of 0.3 to 0.6 Torr, and a treatment time of 5 to 20 minutes; more preferably: a flow ratio of nitrogen to oxygen of 3:7, a power of 20 W, a gas pressure of 0.4 Torr, and a treatment time of 15 minutes.

[0020] Preferably, during the plasma treatment in steps (3) and (4), a mask is used to protect the source-drain electrode contact interface.

[0021] Preferably, the source-drain electrode material in step (5) is aluminum, and the thickness is 100 to 250 nm.

[0022] Preferably, the source-drain electrodes in step (5) are deposited using direct current sputtering technology.

[0023] The present invention adopts a two-step plasma treatment method. The first step is to pre-treat with nitrogen. The chemical activity of nitrogen is relatively low, and it is safer during high-energy treatment. The power and pressure of this step are relatively large, and the energy of the particles is large, which will cause a certain degree of bombardment on the film, forming a high-temperature zone locally, so that the particles can cross the barrier for reconstruction, which plays a role in thermal repair, and thermal expansion will form some microcracks. The maximum temperature will not exceed 100°C, and there is no damage to the flexible substrate. The second step is nitrogen + oxygen mixed gas plasma treatment. The power and pressure of this step are relatively low, so the energy of the plasma is small, and the plasma energy intensity can be further regulated by changing the ratio of the mixed gas; oxygen is highly active after ionization, and oxygen plasma not only reacts on the surface of the film, passivates the dangling bonds and polar groups, but also enters the film along the microcracks formed in the first step. The reaction at 3 to 5 nm, the oxide surface and sub-surface are passivated by the oxygen plasma reaction, and the defect states such as oxygen vacancies and hydrogen interstitials are greatly reduced; the gas reacts on the surface of the film, which can reduce the surface state density, which is conducive to forming a good device contact. At the same time, as the plasma energy decreases (from the first step of high-energy plasma treatment to the second step of low-energy plasma treatment), the temperature of the film surface also decreases, and the microcracks begin to shrink and heal, so after two steps of treatment, the film surface is still smooth. After the two-step plasma treatment, the defect states of several nanolayers on the surface of the oxide film are greatly reduced after reacting with oxygen and nitrogen, which improves the metal oxygen bond strength, reduces the additional carriers on the surface, and inhibits the front channel conduction path; the newly generated trace metal nitride forms a cross-linked network on the surface, which can effectively improve the density, form an ultra-thin barrier layer, and play a role in isolating air water oxygen, inhibiting excess carriers and off-state current of the device. During plasma treatment, a mask is used for regional selective treatment, and the source-drain electrode contact interface is protected, so there is no barrier layer at the electrode contact interface, which will not hinder the device from turning on.

[0024] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0025] The method of the present invention has the advantages of simple equipment, large-area processing, short processing time, and low process temperature. The two-step plasma treatment method can give full play to its optimization effect of energy transfer and interface reaction, effectively combine heat conduction and interface reaction, and successfully prepare high-reliability flexible AOS-TFT at a relatively low process temperature. The low-temperature process will not damage the flexible substrate, and it is generally applicable to improving the reliability of flexible AOS-TFT devices. Compared with traditional methods for improving TFT reliability: passivation layer, interface modification, etc., the use of plasma treatment will not increase the thickness of the device. The thinner the overall thickness of the device, the more conducive to flexible applications. The nitrogen and oxygen used are both commonly used industrial gases, which are compatible with existing processes and are conducive to the rapid realization of technology transfer from laboratories to enterprises. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the two-step plasma treatment process in Example 1.

[0027] Figure 2 Schematic diagram of the TFT device structure in Example 1, wherein 1 is a PI flexible substrate, 2 is a gate, 3 is an insulating layer, 4 is a source and drain electrode, and 5 is an active layer.

[0028] Figure 3 This is the drift result of the bias test of the device in Example 1 that has not been plasma treated.

[0029] Figure 4 This is the device bias test drift result after the two-step plasma treatment in Example 1.

[0030] Figure 5 The bias test results of the TFT device treated with argon gas in the first step in Comparative Example 1 are shown.

[0031] Figure 6 This is the bias test result of the TFT device in Comparative Example 2 that only performs the second step mixed gas treatment.

[0032] Figure 7 This is the bias test result of the TFT device in comparative example 3 in which only oxygen gas is used for the second step.

[0033] Figure 8 This is the bias test result of the TFT device using lower power in the first step of high-energy treatment in Comparative Example 4.

[0034] Fig. 9 This is the bias test result of the TFT device using higher power in the second step low-energy treatment in Comparative Example 5. DETAILED DESCRIPTION

[0035] The present invention is further described in detail below in conjunction with examples and drawings, but the embodiments of the present invention are not limited thereto.

[0036] If no specific conditions are specified in the examples of the present invention, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. All raw materials, reagents, etc., whose manufacturers are not specified, are conventional products that can be purchased commercially.

[0037] Example 1

[0038] A method for improving the reliability of a flexible oxide TFT device by low-temperature plasma post-treatment in this embodiment has the following specific steps:

[0039] (1) Cleaning of polyimide PI substrate: First, irradiate the 10×10 mm PI sheet with ultraviolet light for 120 seconds to decompose the organic pollutants that may exist on the surface. After cleaning, use deionized water for ultrasonic cleaning twice, each time for 15 minutes, to remove water-soluble pollutants; then use isopropanol for ultrasonic cleaning for 15 minutes to remove the remaining pollutants and moisture. Put the substrate into a constant temperature drying oven at 80°C for more than 2 hours to obtain a clean and dry substrate.

[0040] (2) Preparation of gate and insulating layer: A 300nm Al:Nd alloy film is deposited by DC magnetron sputtering and patterned by wet etching to form an Al:Nd alloy (Al:Nd=2:98at%) gate electrode. A portion of the Al:Nd alloy film is oxidized to Al2O3:Nd as an insulating layer by anodization, with an oxidized thickness of about 200nm. The purpose of trace Nd doping is to suppress the thermal expansion of the Al film and reduce the device leakage current.

[0041] (3) Radio frequency magnetron sputtering and mask patterning were performed to prepare an active layer with a thickness of 20 nm. The material was Al-Nd:InZnO target (Al2O3:Nd2O3:In2O3:ZnO=0.63:0.41:88.93:10.03wt%, purity 99.999%).

[0042] (4) The active layer is annealed in an oxygen atmosphere at 200°C for 1 hour and then naturally cooled for 2 hours.

[0043] (5) High-energy nitrogen plasma treatment of the back channel of the oxide active layer, the parameters are: power 70W, gas pressure 0.4Torr, treatment time 10 minutes, during the treatment process, a mask is used to protect the source-drain electrode contact interface.

[0044] (6) Low-energy nitrogen + oxygen mixed gas plasma treatment, the parameters are: nitrogen / oxygen flow ratio of 3:7, power 20 W, gas pressure 0.4 Torr, treatment time 15 minutes, and a mask is used to protect the source-drain electrode contact interface during the treatment process.

[0045] (7) A source-drain electrode with a thickness of 150 nm was prepared by direct current magnetron sputtering and mask patterning, and the material was pure aluminum target (99.999%) to obtain a TFT device.

[0046] In order to eliminate the short-term effects of plasma treatment, the TFT devices were left in air for 24 hours before testing.

[0047] (8) Through the negative bias NBS test, it was found that compared with the device without plasma treatment (no plasma treatment in steps (5)-(6) and other processes were the same), the threshold voltage drift of the device after the two-step plasma treatment was very small, and the device reliability was significantly improved. Figure 3-4 .

[0048] Comparative Example 1

[0049] In the first step of this comparative example, argon plasma treatment is used, and the other processes are the same as those in Example 1. The specific steps are as follows:

[0050] (1) Cleaning of polyimide PI substrate: First, irradiate a 10×10 mm PI sheet with ultraviolet light for 120 seconds to decompose organic pollutants that may exist on the surface. After cleaning, ultrasonically clean it twice with deionized water, each time for 15 minutes, to remove water-soluble pollutants; then ultrasonically clean it with isopropanol for 15 minutes once to remove remaining pollutants and moisture. Place the substrate in a constant temperature drying oven at 80°C for more than 2 hours to obtain a clean and dry substrate.

[0051] (2) Preparation of gate and insulating layer: A 300nm Al:Nd alloy film is deposited by DC magnetron sputtering and patterned by wet etching to form an Al:Nd alloy (Al:Nd=2:98at%) gate electrode. A portion of the Al:Nd alloy film is oxidized to Al2O3:Nd as an insulating layer by anodization, with an oxidized thickness of about 200nm. The purpose of trace Nd doping is to suppress the thermal expansion of the Al film and reduce the device leakage current.

[0052] (3) Radio frequency magnetron sputtering and mask patterning were performed to prepare an active layer with a thickness of 20 nm. The material was Al-Nd:InZnO target (Al2O3:Nd2O3:In2O3:ZnO=0.63:0.41:88.93:10.03wt%, purity 99.999%).

[0053] (4) The active layer is annealed in an oxygen atmosphere at 200°C for 1 hour and then naturally cooled for 2 hours.

[0054] (5) The back channel of the oxide active layer is treated with high-energy argon plasma. The parameters are: power 70 W, gas pressure 0.4 Torr, and treatment time 10 minutes. During the treatment process, a mask is used to protect the source-drain electrode contact interface.

[0055] (6) Low-energy nitrogen + oxygen mixed gas plasma treatment, the parameters are: nitrogen / oxygen flow ratio of 3:7, power 20 W, gas pressure 0.4 Torr, treatment time 15 minutes, and a mask is used to protect the source-drain electrode contact interface during the treatment process.

[0056] (7) DC magnetron sputtering and mask patterning method are used, the thickness is 150nm, and the material is pure aluminum target (99.999%).

[0057] In order to eliminate the short-term effects of plasma treatment, the TFT devices were left in air for 24 hours before testing.

[0058] (8) Through the negative bias NBS test, it was found that compared with the device without plasma treatment (the plasma treatment of steps (5)-(6) was not performed, and the other processes were the same), the threshold voltage drift of the device after the two-step plasma treatment in this comparative example was reduced, the device stability was improved to a limited extent, the subthreshold swing SS of the TFT transfer curve was relatively large, and the rising trend of the curve was not as steep as that of Example 1, indicating that the first step of argon plasma treatment caused obvious damage to the semiconductor, resulting in the deterioration of the device performance. Figure 5 , the effect is not as significant as that of Example 1.

[0059] Comparative Example 2

[0060] This comparative example only performs the first step of nitrogen plasma treatment, and the other processes are compared with Example 1, and the specific steps are as follows:

[0061] (1) Cleaning of polyimide PI substrate: First, irradiate a 10×10 mm PI sheet with ultraviolet light for 120 seconds to decompose organic pollutants that may exist on the surface. After cleaning, ultrasonically clean it twice with deionized water, each time for 15 minutes, to remove water-soluble pollutants; then ultrasonically clean it with isopropanol for 15 minutes once to remove remaining pollutants and moisture. Place the substrate in a constant temperature drying oven at 80°C for more than 2 hours to obtain a clean and dry substrate.

[0062] (2) Preparation of gate and insulating layer: A 300nm Al:Nd alloy film is deposited by DC magnetron sputtering and patterned by wet etching to form an Al:Nd alloy (Al:Nd=2:98at%) gate electrode. A portion of the Al:Nd alloy film is oxidized to Al2O3:Nd as an insulating layer by anodization, with an oxidized thickness of about 200nm. The purpose of trace Nd doping is to suppress the thermal expansion of the Al film and reduce the device leakage current.

[0063] (3) Radio frequency magnetron sputtering and mask patterning were performed to prepare an active layer with a thickness of 20 nm. The material was Al-Nd:InZnO target (Al2O3:Nd2O3:In2O3:ZnO=0.63:0.41:88.93:10.03wt%, purity 99.999%).

[0064] (4) The active layer is annealed in an oxygen atmosphere at 200°C for 1 hour and then naturally cooled for 2 hours.

[0065] (5) High-energy nitrogen plasma treatment of the back channel of the oxide active layer, the parameters are: power 70W, gas pressure 0.4Torr, treatment time 10 minutes, during the treatment process, a mask is used to protect the source-drain electrode contact interface.

[0066] (6) DC magnetron sputtering and mask patterning method are used, the thickness is 150nm, and the material is pure aluminum target (99.999%).

[0067] In order to eliminate the short-term effects of plasma treatment, the TFT devices were left in air for 24 hours before testing.

[0068] (7) Through the gate bias PBS test, it was found that compared with the device that was not plasma treated (the plasma treatment in step (5) was not performed, and other processes were the same), the threshold voltage drift phenomenon of the TFT device was very serious and the device performance deteriorated.

[0069] Comparative Example 3

[0070] In the second step of this comparative example, only oxygen is used, but no nitrogen is used. The other processes are the same as those in Example 1. The specific steps are as follows:

[0071] (1) Cleaning of polyimide PI substrate: First, irradiate a 10×10 mm PI sheet with ultraviolet light for 120 seconds to decompose organic pollutants that may exist on the surface. After cleaning, ultrasonically clean it twice with deionized water, each time for 15 minutes, to remove water-soluble pollutants; then ultrasonically clean it with isopropanol for 15 minutes once to remove remaining pollutants and moisture. Place the substrate in a constant temperature drying oven at 80°C for more than 2 hours to obtain a clean and dry substrate.

[0072] (2) Preparation of gate and insulating layer: A 300nm Al:Nd alloy film is deposited by DC magnetron sputtering and patterned by wet etching to form an Al:Nd alloy (Al:Nd=2:98at%) gate electrode. A portion of the Al:Nd alloy film is oxidized to Al2O3:Nd as an insulating layer by anodization, with an oxidized thickness of about 200nm. The purpose of trace Nd doping is to suppress the thermal expansion of the Al film and reduce the device leakage current.

[0073] (3) Radio frequency magnetron sputtering and mask patterning were performed to prepare an active layer with a thickness of 20 nm. The material was Al-Nd:InZnO target (Al2O3:Nd2O3:In2O3:ZnO=0.63:0.41:88.93:10.03wt%, purity 99.999%).

[0074] (4) The active layer is annealed in an oxygen atmosphere at 200°C for 1 hour and then naturally cooled for 2 hours.

[0075] (5) High-energy nitrogen plasma treatment of the back channel of the oxide active layer, the parameters are: power 70W, gas pressure 0.4Torr, treatment time 10 minutes, during the treatment process, a mask is used to protect the source-drain electrode contact interface.

[0076] (6) Low-energy oxygen plasma treatment of the back channel of the oxide active layer, the parameters are: power 20W, gas pressure 0.4Torr, treatment time 15 minutes, during the treatment process, a mask is used to protect the source-drain electrode contact interface.

[0077] (7) DC magnetron sputtering and mask patterning method are used, the thickness is 150nm, and the material is pure aluminum target (99.999%).

[0078] In order to eliminate the short-term effects of plasma treatment, the TFT devices were left in air for 24 hours before testing.

[0079] (8) Through the gate bias PBS test, it was found that compared with the device that was not plasma treated (the plasma treatment of steps (5)-(6) was not performed, and the other processes were the same), the threshold voltage drift phenomenon of the TFT device was smaller, but the SS was larger, the rising edge was not steep, the response speed was slow, and the retrace hysteresis was large.

[0080] Comparative Example 4

[0081] In this comparative example, a relatively low power of 50 W is used in the first step of high energy treatment, and the other processes are the same as those in Example 1. The specific steps are as follows:

[0082] (1) Cleaning of polyimide PI substrate: First, irradiate a 10×10 mm PI sheet with ultraviolet light for 120 seconds to decompose organic pollutants that may exist on the surface. After cleaning, ultrasonically clean it twice with deionized water, each time for 15 minutes, to remove water-soluble pollutants; then ultrasonically clean it with isopropanol for 15 minutes once to remove remaining pollutants and moisture. Place the substrate in a constant temperature drying oven at 80°C for more than 2 hours to obtain a clean and dry substrate.

[0083] (2) Preparation of gate and insulating layer: A 300nm Al:Nd alloy film is deposited by DC magnetron sputtering and patterned by wet etching to form an Al:Nd alloy (Al:Nd=2:98at%) gate electrode. A portion of the Al:Nd alloy film is oxidized to Al2O3:Nd as an insulating layer by anodization, with an oxidized thickness of about 200nm. The purpose of trace Nd doping is to suppress the thermal expansion of the Al film and reduce the device leakage current.

[0084] (3) Radio frequency magnetron sputtering and mask patterning were performed to prepare an active layer with a thickness of 20 nm. The material was Al-Nd:InZnO target (Al2O3:Nd2O3:In2O3:ZnO=0.63:0.41:88.93:10.03wt%, purity 99.999%).

[0085] (4) The active layer is annealed in an oxygen atmosphere at 200°C for 1 hour and then naturally cooled for 2 hours.

[0086] (5) High-energy nitrogen plasma treatment of the back channel of the oxide active layer, the parameters are: power 50W, gas pressure 0.4Torr, treatment time 10 minutes, during the treatment process, a mask is used to protect the source-drain electrode contact interface.

[0087] (6) Low-energy nitrogen + oxygen plasma treatment of the oxide active layer back channel, the parameters are: power 20W, gas pressure 0.4Torr, treatment time 15 minutes, during the treatment process, a mask is used to protect the source-drain electrode contact interface.

[0088] (7) DC magnetron sputtering and mask patterning method are used, the thickness is 150nm, and the material is pure aluminum target (99.999%).

[0089] In order to eliminate the short-term effects of plasma treatment, the TFT devices were left in air for 24 hours before testing.

[0090] (8) Through the gate bias PBS test, it was found that compared with the device without plasma treatment (no plasma treatment in steps (5)-(6) and other processes were the same),

[0091] There is no obvious improvement in performance because the first step of processing power is small and the ion energy is insufficient to achieve the corresponding effect.

[0092] Comparative Example 5

[0093] In the second step of low-energy treatment in this comparative example, a higher power of 60W is used, and the other processes are the same as those in Example 1. The specific steps are as follows:

[0094] (1) Cleaning of polyimide PI substrate: First, irradiate a 10×10 mm PI sheet with ultraviolet light for 120 seconds to decompose organic pollutants that may exist on the surface. After cleaning, ultrasonically clean it twice with deionized water, each time for 15 minutes, to remove water-soluble pollutants; then ultrasonically clean it with isopropanol for 15 minutes once to remove remaining pollutants and moisture. Place the substrate in a constant temperature drying oven at 80°C for more than 2 hours to obtain a clean and dry substrate.

[0095] (2) Preparation of gate and insulating layer: A 300nm Al:Nd alloy film is deposited by DC magnetron sputtering and patterned by wet etching to form an Al:Nd alloy (Al:Nd=2:98at%) gate electrode. A portion of the Al:Nd alloy film is oxidized to Al2O3:Nd as an insulating layer by anodization, with an oxidized thickness of about 200nm. The purpose of trace Nd doping is to suppress the thermal expansion of the Al film and reduce the device leakage current.

[0096] (3) Radio frequency magnetron sputtering and mask patterning were performed to prepare an active layer with a thickness of 20 nm. The material was Al-Nd:InZnO target (Al2O3:Nd2O3:In2O3:ZnO=0.63:0.41:88.93:10.03wt%, purity 99.999%).

[0097] (4) The active layer is annealed in an oxygen atmosphere at 200°C for 1 hour and then naturally cooled for 2 hours.

[0098] (5) High-energy nitrogen plasma treatment of the back channel of the oxide active layer, the parameters are: power 70W, gas pressure 0.4Torr, treatment time 10 minutes, during the treatment process, a mask is used to protect the source-drain electrode contact interface.

[0099] (6) High-energy nitrogen + oxygen plasma treatment of the oxide active layer back channel, the parameters are: power 60W, gas pressure 0.4Torr, treatment time 15 minutes, during the treatment process, a mask is used to protect the source-drain electrode contact interface.

[0100] (7) DC magnetron sputtering and mask patterning method are used, the thickness is 150nm, and the material is pure aluminum target (99.999%).

[0101] In order to eliminate the short-term effects of plasma treatment, the TFT devices were left in air for 24 hours before testing.

[0102] (8) Through the gate bias test, it was found that compared with the device that was not plasma treated (the plasma treatment of steps (5)-(6) was not performed, and the other processes were the same), the device performance deteriorated and the threshold voltage drift became larger. This shows that the power of the second step low-energy treatment in this comparative example is too large. Through comparative examples 4 and 5, the importance and uniqueness of the power range selection of the two-step plasma treatment are further explained.

[0103] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for improving the reliability of a flexible oxide TFT device by low temperature plasma post-treatment, characterized in that: The following steps are involved: (1) depositing a metal film on a substrate as a gate, oxidizing part of the metal film into an oxide film as an insulating layer, and then using a mask patterning method to prepare an active layer; (2) annealing the active layer of step (1) at 100 to 300° C. in an oxygen atmosphere for 1 to 3 hours; (3) treating the back channel of the active layer after annealing in step (2) using high energy nitrogen plasma; (4) treating the back channel of the active layer obtained in step (3) with a mixed gas plasma of low-energy nitrogen and oxygen; (5) preparing source and drain electrodes on the back channel of the active layer by using a mask patterning method to obtain a TFT device; The conditions of the low-energy nitrogen and oxygen mixed gas plasma treatment in step (4) are: a flow ratio of nitrogen to oxygen of 1:9 to 1:1, a power of 10 to 50 W, a gas pressure of 0.3 to 0.6 Torr, and a treatment time of 5 to 20 minutes; The conditions of the high-energy nitrogen plasma treatment in step (3) are: power 60-100 W, gas pressure 0.3-0.6 Torr, and treatment time 5-30 minutes.

2. The method for improving the reliability of a flexible oxide TFT device by low temperature plasma post-treatment according to claim 1, characterized in that: The conditions of the high-energy nitrogen plasma treatment in step (3) are: power 70 W, pressure 0.4 Torr, and treatment time 5 minutes; The conditions for the low-energy nitrogen and oxygen mixed gas plasma treatment in step (4) are: a flow ratio of nitrogen to oxygen of 3:7, a power of 20 W, a gas pressure of 0.4 Torr, and a treatment time of 15 minutes.

3. The method for improving the reliability of a flexible oxide TFT device by low temperature plasma post-treatment according to claim 1, characterized in that: The active layer material in step (1) is Al-Nd:InZnO, and has a thickness of 10 to 30 nm.

4. The method for improving the reliability of a flexible oxide TFT device by low temperature plasma post-treatment according to claim 1, characterized in that: The material of the metal film in step (1) is Al-Nd alloy; the thickness of the gate is 100 to 400 nm.

5. The method for improving the reliability of a flexible oxide TFT device by low temperature plasma post-treatment according to claim 1, characterized in that: The thickness of the insulating layer in step (1) is 100 to 300 nm.

6. The method for improving the reliability of a flexible oxide TFT device by low temperature plasma post-treatment according to claim 1, characterized in that: The source-drain electrode material in step (5) is aluminum, and the thickness is 100 to 250 nm.

7. The method for improving the reliability of a flexible oxide TFT device by low temperature plasma post-treatment according to claim 1, characterized in that: The annealing treatment in step (2) is performed at a temperature of 200° C. and for a period of 1 hour.

8. The method for improving the reliability of a flexible oxide TFT device by low temperature plasma post-treatment according to claim 1, characterized in that: The substrate in step (1) is a polyimide substrate; during the plasma treatment in steps (3) and (4), a mask is used to protect the source-drain electrode contact interface.

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