Aluminum oxide thin film for thin film transistor, double-layer passivation film and preparation method of double-layer passivation film

Abstract

The invention relates to the technical field of thin film preparation, and discloses an aluminum oxide thin film for a thin film transistor, a double-layer passivation film and a preparation method thereof. The preparation method of the aluminum oxide thin film comprises the following steps: vacuumizing and heating an atomic layer deposition system chamber, and preserving heat of a thin film transistor; the method comprises the following steps: heating one of an aluminum precursor source tri (dimethylamino) aluminum, aluminum triisopropoxide, aluminum triethoxy, tri (diethylamino) aluminum, aluminum tri-sec-butoxide, aluminum trichloride, tri (diisopropyl amino) aluminum, triethyl aluminum or aluminum tri-sec-butoxide; and an aluminum precursor source, inert gas and an oxygen source are introduced, the inert gas forms deposition circulation, and the aluminum oxide film is obtained on the thin film transistor after annealing. The low-activity aluminum precursor source is used for depositing the aluminum oxide thin film, damage to the channel layer is effectively avoided, the double-layer passivation film based on the aluminum oxide thin film can effectively package the oxide thin film transistor, the thin film transistor is isolated from molecules in the atmosphere, and the stability of the channel layer is enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of thin film preparation, and in particular to an aluminum oxide thin film for a thin film transistor, a double-layer passivation film and a preparation method thereof. Background Art

[0002] Oxide thin-film transistors (TFTs) have the advantages of high field-effect mobility, low off-state current, good uniformity, and a low thermal budget. They have great application potential in new display technologies, three-dimensional integrated circuits, flexible and wearable electronic devices, and other fields. In practical applications, TFTs often operate under certain stresses for long periods of time, so the stability of thin-film transistors (TFTs) is extremely important. However, oxide channels are often sensitive to the environment. The adsorption and desorption of gas molecules such as oxygen and water on the channel surface can easily degrade electrical stability, limiting their wider application.

[0003] Preparing a passivation layer on the surface of an oxide thin film transistor is one of the important methods to improve the stability of the device. Currently, the commonly used methods for preparing passivation films include plasma-enhanced chemical vapor deposition, electron beam evaporation coating, magnetron sputtering, atomic layer deposition, etc. Among them, the atomic layer deposition technology deposits the substance layer by layer in the form of a single atomic film on the substrate surface by alternately introducing a gaseous precursor. Due to its self-limiting and complementary nature, this method can accurately control the thickness of the passivation layer, and at the same time has excellent thin film composition control capabilities, and can prepare a passivation layer with good conformality, uniform thickness, and dense and non-porous properties.

[0004] The aluminum oxide (Al2O3) film deposited by atomic layer deposition has a high dielectric constant and low leakage current, and is an excellent oxygen and water vapor barrier material. It is widely used in the insulating layer and passivation layer materials of various devices. For example, patent (CN114420790A) discloses a process for growing a laminated aluminum oxide passivation layer using atomic layer deposition technology, in which trimethylaluminum (TMA) is used as the aluminum source. Patent (CN116666501A) discloses a method for growing a denser aluminum oxide passivation layer by utilizing atomic layer deposition technology, still using trimethylaluminum as the aluminum source. It can be seen that the method of preparing an aluminum oxide passivation layer by atomic layer deposition technology using trimethylaluminum as the aluminum source is widely used.

[0005] However, when trimethylaluminum is used as an aluminum source to passivate thin-film transistors, due to its high activity, transistors with oxides such as indium oxide, gallium oxide, and zinc oxide as the main channel components will react with trimethylaluminum as follows:

[0006] In2O3+2Al(CH3)3(g)=Al2O3+2In(CH3)3(g)(ΔG=-317kcal)

[0007] 3ZnO+2Al(CH3)3(g)=Al2O3+3Zn(CH3)2(g)(ΔG=-164kcal)

[0008] Ga2O3+2Al(CH3)3(g)=Al2O3+2Ga(CH3)3(g)(ΔG=-173kcal)

[0009] These reactions with negative Gibbs free energy changes tend to proceed spontaneously thermodynamically, resulting in reverse etching of the channel layer material, severely damaging it. Therefore, trimethylaluminum cannot be directly used as an aluminum source for passivation layer growth. Therefore, to reduce channel damage, it is necessary to find a suitable, less reactive aluminum source while also ensuring high-quality films to effectively isolate molecules such as water and oxygen.

[0010] Therefore, the existing technology still needs to be improved and developed. Summary of the Invention

[0011] In view of the above-mentioned deficiencies in the prior art, the present invention provides an aluminum oxide thin film, a double-layer passivation film and a preparation method thereof for thin film transistors, aiming to solve the problem of etching damage to the channel layer in the thin film transistor when trimethylaluminum is used as the aluminum source in the existing technology for preparing aluminum oxide thin films.

[0012] Specifically, the technical solutions of the present invention are as follows:

[0013] In a first aspect, the present invention provides a method for preparing an aluminum oxide thin film for a thin film transistor, comprising the steps of:

[0014] (1) After the chamber of the atomic layer deposition system is evacuated, it is heated, and a thin film transistor is placed in the chamber to keep it warm;

[0015] (2) heating an aluminum precursor source, wherein the aluminum precursor source is one of tris(dimethylamino)aluminum, aluminum triisopropoxide, triethoxyaluminum, tris(diethylamino)aluminum, aluminum tri-sec-butoxide, aluminum trichloride, tris(diisopropylamino)aluminum, triethylaluminum, and aluminum tri-sec-butoxide;

[0016] (3) adjusting the chamber pressure, sequentially introducing the aluminum precursor source, the inert gas, the oxygen source, and the inert gas into the chamber to form a deposition cycle, and repeating the deposition cycle;

[0017] (4) Annealing the thin film transistor processed in step (3) to obtain the aluminum oxide thin film on the thin film transistor.

[0018] In step (1), optionally, the temperature of heating the atomic layer deposition chamber is 50 to 500°C.

[0019] In step (1), optionally, the thin film transistor includes a substrate, a gate electrode, a gate dielectric, a source electrode, a drain electrode and an oxide active layer, and the oxide active layer is selected from one of indium gallium zinc oxide, indium oxide, zinc oxide, gallium oxide, tin oxide, indium gallium oxide, indium zinc oxide, zinc gallium oxide, indium gallium tin oxide or indium tin zinc oxide; and the thin film transistor is kept warm in the chamber for 30 seconds to 3 hours.

[0020] In step (2), optionally, the temperature at which the aluminum precursor source is heated is 25 to 180°C.

[0021] In step (3), optionally, the time for introducing the aluminum precursor source is 0.1 to 20 seconds, the time for introducing the oxygen source is 0.1 to 20 seconds, and the time for introducing the inert gas is 1 to 60 seconds;

[0022] Optionally, the inert gas is high-purity nitrogen or high-purity argon;

[0023] Optionally, the oxygen source is one of ozone, water, oxygen, nitrous oxide, nitrogen dioxide, nitrogen tetroxide, fatty alcohol or oxygen plasma.

[0024] In step (3), optionally, the deposition cycle is repeated 5 to 1000 times, and the thickness of the aluminum oxide film is 0.5 to 100 nm.

[0025] In step (4), optionally, the annealing temperature is 100 to 500° C., and the annealing time is 0 to 240 minutes.

[0026] In a second aspect, the present invention provides an aluminum oxide thin film for a thin film transistor, which is prepared by the method for preparing the aluminum oxide thin film for a thin film transistor.

[0027] In a third aspect, the present invention provides a double-layer passivation film, comprising a bottom passivation film and an outer passivation film, wherein the bottom passivation film is the aluminum oxide thin film for thin film transistors, and the outer passivation film is prepared on the surface of the aluminum oxide thin film;

[0028] Optionally, the outer passivation film is any one of an aluminum oxide film, a titanium oxide film, a hafnium oxide film, a yttrium oxide film, a silicon oxide film and a silicon nitride film.

[0029] Optionally, the outer passivation film is prepared by adopting one of atomic layer deposition technology, plasma assisted atomic layer deposition technology, chemical vapor deposition technology and plasma enhanced chemical vapor deposition technology.

[0030] Beneficial effects:

[0031] The present invention provides an aluminum oxide film, a double-layer passivation film and a preparation method thereof for a thin film transistor. The aluminum oxide film is prepared by using a low-activity aluminum precursor source such as tri(dimethylamino)aluminum, triisopropoxide aluminum, triethoxyaluminum, and tri(diethylamino)aluminum in an atomic layer deposition technique, thereby solving the problem in the prior art that trimethylaluminum is easily damaged by a replacement reaction with the oxide channel layer of the thin film transistor. The present invention effectively avoids damage to the channel layer by using a process for depositing an aluminum oxide film using a low-activity aluminum precursor source. Furthermore, a double-layer passivation film can be obtained by further preparing an outer passivation film on the surface of the aluminum oxide film. The passivation film with a double-layer structure can effectively encapsulate the oxide thin film transistor, isolate the thin film transistor from molecules in the atmosphere, enhance the stability of the channel layer, and have high controllability and operability. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic structural diagram of the bottom-gate thin film transistor provided by the present invention.

[0033] Figure 2 This is a schematic diagram of the overall structure of the thin film transistor after depositing a double-layer passivation film provided by the present invention.

[0034] Figure 3 This is a top view of the overall structure of the thin film transistor after depositing a double-layer passivation film provided in Example 1 of the present invention.

[0035] Figure 4 This is the transfer curve of the bottom-gate thin-film transistor before growing a double-layer passivation film (double-layer aluminum oxide film) in Example 1 of the present invention.

[0036] Figure 5 This is the transfer curve of the bottom-gate thin-film transistor after growing a double-layer passivation film (double-layer aluminum oxide film) in Example 1 of the present invention.

[0037] Figure 6 This is the transfer curve of the bottom-gate thin-film transistor before growing the aluminum oxide film in Example 2 of the present invention.

[0038] Figure 7 This is the transfer curve of the bottom-gate thin-film transistor after growing the aluminum oxide film in Example 2 of the present invention.

[0039] Figure 8 This is the transfer curve of the bottom-gate thin-film transistor before growing a double-layer passivation film (aluminum oxide film and hafnium oxide film) in Example 3 of the present invention.

[0040] Figure 9 The transfer curve of the bottom-gate thin film transistor after growing a double-layer passivation film (aluminum oxide film and hafnium oxide film) in Example 3 of the present invention is shown in FIG.

[0041] Figure 10This is the transfer curve of the bottom-gate thin film transistor before growing the aluminum oxide film in Comparative Example 1 of the present invention.

[0042] Figure 11 This is the transfer curve of the bottom-gate thin film transistor after growing the aluminum oxide film in Comparative Example 1 of the present invention.

[0043] Figure 12 This is the transfer curve of the bottom-gate thin film transistor before growing the hafnium oxide film in Comparative Example 2 of the present invention.

[0044] Figure 13 The transfer curve of the bottom-gate thin film transistor after growing the hafnium oxide film in comparative example 2 of the present invention is shown in FIG. DETAILED DESCRIPTION

[0045] The present invention provides an aluminum oxide thin film, a double-layer passivation film, and a method for preparing the same for thin-film transistors. To clarify the objectives, technical solutions, and effects of the present invention, the present invention is described in further detail below. It should be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the scope of protection of the present invention.

[0046] An embodiment of the present invention provides a method for preparing an aluminum oxide thin film for a thin film transistor, comprising the steps of:

[0047] (1) After the chamber of the atomic layer deposition system is evacuated, it is heated, and a thin film transistor is placed in the chamber to keep it warm;

[0048] (2) heating an aluminum precursor source, wherein the aluminum precursor source is one of tris(dimethylamino)aluminum, aluminum triisopropoxide, triethoxyaluminum, tris(diethylamino)aluminum, aluminum tri-sec-butoxide, aluminum trichloride, tris(diisopropylamino)aluminum, triethylaluminum, and aluminum tri-sec-butoxide;

[0049] (3) adjusting the chamber pressure, sequentially introducing the aluminum precursor source, the inert gas, the oxygen source, and the inert gas into the chamber to form a deposition cycle, and repeating the deposition cycle;

[0050] (4) Annealing the thin film transistor processed in step (3) to obtain the aluminum oxide thin film on the thin film transistor.

[0051] In step (1), in some embodiments, the temperature of the ALD chamber is heated to 50° C. to 500° C. If the heating temperature is lower than 50° C., the low-activity aluminum precursor, such as tris(dimethylamino)aluminum, cannot fully react with the oxygen source; and if the heating temperature is higher than 500° C., the precursor may thermally decompose.

[0052] In some embodiments, the structural diagram of the thin film transistor is as follows Figure 1As shown, it includes 1 substrate, 2 gate electrodes, 3 gate dielectrics, 4 source and drain electrodes, and 5 oxide active layer.

[0053] In some embodiments, the oxide active layer is selected from one of indium gallium zinc oxide, indium oxide, zinc oxide, gallium oxide, tin oxide, indium gallium oxide, indium zinc oxide, zinc gallium oxide, indium gallium tin oxide, or indium tin zinc oxide.

[0054] In step (1), in some embodiments, the thin film transistor is kept warm in the chamber for 30 seconds to 3 hours.

[0055] In step (2), in some embodiments, the temperature for heating the aluminum precursor source is 25 to 180° C. For example, when the aluminum precursor source is tris(dimethylamino)aluminum, the preferred heating temperature is 50 to 100° C.; when the aluminum precursor source is aluminum triisopropoxide, the preferred heating temperature is 80 to 130° C.

[0056] In step (3), in some embodiments, the time for introducing the aluminum precursor source is 0.1 to 20 seconds, the time for introducing the oxygen source is 0.1 to 20 seconds, and the time for introducing the inert gas is 1 to 60 seconds. The time for introducing the aluminum precursor source and the oxygen source is to ensure sufficient flux without causing excessive waste. At the same time, the time for introducing the inert gas is to ensure that the aluminum precursor source in the previous cycle is purged clean before introducing the next aluminum precursor source, so as to achieve atomic-level layer-by-layer deposition.

[0057] In some embodiments, the inert gas is high-purity nitrogen or high-purity argon.

[0058] In some embodiments, the oxygen source is one of ozone, water, oxygen, nitrous oxide, nitrogen dioxide, nitrogen tetroxide, aliphatic alcohol, or oxygen plasma.

[0059] In step (3), in some embodiments, the deposition cycle is repeated 5 to 1000 times, and the thickness of the aluminum oxide film is 0.5 to 100 nm. Unlike chemical vapor deposition methods, which generally require micron-scale films to achieve passivation, atomic layer deposition methods can achieve excellent passivation effects even with thin nanometer-scale films due to their ability to ensure excellent film quality.

[0060] In a preferred embodiment, the deposition cycle is repeated 5 to 200 times, and the thickness of the aluminum oxide film is 1 to 20 nm.

[0061] In step (4), in some embodiments, the annealing temperature is 100 to 500° C., and the annealing time is 0 to 240 minutes. In a preferred embodiment, the annealing time is 30 to 240 minutes. The annealing treatment can be performed in an atmosphere such as air, nitrogen, or oxygen. Through the annealing treatment, the interface between the active layer and the passivation layer of the transistor can be repaired, defects and impurities in the active layer and the interface can be reduced, and the impurities can be more evenly distributed, thereby improving the electrical performance and reliability of the transistor.

[0062] An embodiment of the present invention provides an aluminum oxide thin film for a thin film transistor, which is prepared by the method for preparing the aluminum oxide thin film for a thin film transistor.

[0063] An embodiment of the present invention provides a double-layer passivation film, which includes a bottom passivation film and an outer passivation film. The bottom passivation film is the aluminum oxide film for thin film transistors, and the outer passivation film is prepared on the surface of the aluminum oxide film.

[0064] The schematic diagram and top view of the overall structure of the thin film transistor after double-layer passivation can be referred to Figure 2 and Figure 3 The embodiment of the present invention first uses a specific aluminum precursor source to deposit an aluminum oxide film on the oxide active layer (channel layer) of the thin film transistor, and then prepares an outer passivation film on the surface of the aluminum oxide film to construct a double-layer passivation layer.

[0065] In the embodiment of the present invention, after a double-layer passivation film is deposited on the oxide active layer (channel layer) of the thin film transistor, the overall structure of the passivated thin film transistor is as follows: Figure 2 As shown, it includes 1 substrate, 2 gate electrode, 3 gate dielectric, 4 source and drain electrodes, 5 oxide active layer, 6 aluminum oxide film and 7 outer passivation film. The top view of the overall structure of the thin film transistor after passivation can be referred to Figure 3 .

[0066] In some embodiments, the outer passivation film is any one of an aluminum oxide film, a titanium oxide film, a hafnium oxide film, a zirconium oxide film, a yttrium oxide film, a silicon oxide film, and a silicon nitride film. These materials are commonly used oxide transistor passivation layer materials. Growing the outer passivation film on the basis of the aluminum oxide film as the underlying passivation film can reduce damage to the channel caused by the highly active precursor source or plasma used during the growth of the outer passivation film.

[0067] In some embodiments, the outer passivation film is prepared by adopting one of atomic layer deposition technology, plasma-assisted atomic layer deposition technology, chemical vapor deposition technology and plasma-enhanced chemical vapor deposition technology.

[0068] The scheme of the present invention is further described below with reference to specific embodiments.

[0069] Example 1

[0070] In this embodiment, tri(dimethylamino)aluminum and trimethylaluminum are used as aluminum sources for the aluminum oxide film to grow an aluminum oxide film with a thickness of 5 nm. The tri(dimethylamino)aluminum film is 4 nm thick and the trimethylaluminum film is 1 nm thick.

[0071] The bottom-gate TFT selected has an oxide active layer (ie, channel layer) with a length of 20 microns and a width of 50 microns, and the channel layer uses 4nm thick indium oxide.

[0072] The specific steps are as follows:

[0073] Step 1: Preheat the components of the atomic layer deposition equipment:

[0074] (1) Start the vacuum system of the atomic layer deposition equipment and evacuate the chamber;

[0075] (2) heating the atomic layer deposition chamber to 150°C; heating the tri(dimethylamino)aluminum precursor source bottle and pipeline to 70°C; heating the trimethylaluminum precursor source bottle and pipeline to 30°C;

[0076] (3) After sufficient preheating, the prepared indium oxide thin film transistor sample is placed in the atomic layer deposition chamber and kept warm for 0.5 h.

[0077] Step 2: Growing the first layer of aluminum oxide film

[0078] (1) Turn on the inert purge gas and adjust the chamber pressure to 400 mTorr;

[0079] (2) Opening the atomic layer deposition control program, performing 50 deposition cycles, and in each cycle, introducing tri(dimethylamino)aluminum-nitrogen purge gas-ozone-nitrogen purge gas in sequence;

[0080] (3) The aluminum source pulse duration is 3 s, the inert gas purge is 25 s, the ozone pulse duration is 5 s, and the inert gas purge is 30 s.

[0081] Step 3: Growing the second layer of aluminum oxide film

[0082] (1) 10 deposition cycles were performed, and in each cycle, trimethylaluminum-nitrogen purge gas-ozone-nitrogen purge gas was introduced in sequence;

[0083] (2) The aluminum source pulse duration was 2 s, and the inert gas purge was 25 s; the oxygen source pulse duration was 5 s, and the inert gas purge was 30 s.

[0084] Step 4: Annealing

[0085] The device was annealed in air at 200°C for 40 minutes.

[0086] Example 2

[0087] In this embodiment, aluminum triisopropoxide is used as the aluminum source for the aluminum oxide film, and the growth thickness is 5 nm.

[0088] The bottom-gate TFT selected has a channel layer length of 10 microns and a width of 20 microns, and the channel layer uses 4nm thick indium oxide.

[0089] Specific steps:

[0090] Step 1: Preheat the components of the atomic layer deposition equipment:

[0091] (1) Start the vacuum system of the atomic layer deposition equipment and evacuate the chamber;

[0092] (2) heating the atomic layer deposition chamber to 120°C; heating the aluminum triisopropoxide precursor source bottle and pipeline to 110°C;

[0093] (3) After sufficient preheating, the prepared indium oxide thin film transistor sample is placed in the atomic layer deposition chamber and kept warm for 0.5 h.

[0094] Step 2: Growing aluminum oxide film

[0095] (1) Turn on the inert purge gas and adjust the chamber pressure to 400 mTorr;

[0096] (2) Opening the atomic layer deposition control program, performing 80 deposition cycles, and in each cycle, introducing aluminum triisopropoxide-nitrogen purge gas-ozone-nitrogen purge gas in sequence;

[0097] (3) The aluminum source pulse duration is 4 s, the inert gas purge is 35 s, the ozone pulse duration is 5 s, and the inert gas purge is 30 s.

[0098] Step 3: Annealing

[0099] The device was annealed in air at 200°C for 40 minutes.

[0100] Example 3

[0101] In this embodiment, tri(dimethylamino)aluminum and tetra(ethylmethylamino)hafnium are used as precursor sources for a double-layer passivation film to grow a passivation film with a thickness of 7nm. Among them, tri(dimethylamino)aluminum grows a 4nm aluminum oxide film, and tetra(ethylmethylamino)hafnium grows a 3nm hafnium oxide film.

[0102] The bottom-gate TFT selected has an oxide active layer (ie, channel layer) with a length of 20 microns and a width of 50 microns, and the channel layer is made of 3nm thick indium oxide.

[0103] The specific steps are as follows:

[0104] Step 1: Preheat the components of the atomic layer deposition equipment:

[0105] (1) Start the vacuum system of the atomic layer deposition equipment and evacuate the chamber;

[0106] (2) heating the atomic layer deposition chamber to 120°C; heating the tris(dimethylamino)aluminum and tetra(ethylmethylamino)hafnium precursor source bottles and pipes to 70°C;

[0107] (3) After sufficient preheating, the prepared indium oxide thin film transistor sample is placed in the atomic layer deposition chamber and kept warm for 0.5 h.

[0108] Step 2: Grow the first layer of aluminum oxide passivation film

[0109] (1) Turn on the inert purge gas and adjust the chamber pressure to 400 mTorr;

[0110] (2) Opening the atomic layer deposition control program, performing 50 deposition cycles, and in each cycle, introducing tri(dimethylamino)aluminum-nitrogen purge gas-ozone-nitrogen purge gas in sequence;

[0111] (3) The aluminum source pulse duration is 4 s, the inert gas purge is 25 s, the ozone pulse duration is 5 s, and the inert gas purge is 30 s.

[0112] Step 3: Annealing

[0113] The device was annealed in air at 200°C for 40 minutes.

[0114] Step 4: Grow the second layer of hafnium oxide passivation film

[0115] (1) 30 deposition cycles were performed, and in each cycle, tetrakis(ethylmethylamino)hafnium-nitrogen purge gas-ozone-nitrogen purge gas was introduced in sequence;

[0116] (2) The hafnium source pulse duration is 2 s, and the inert gas purge is 25 s. The oxygen source pulse duration is 5 s, and the inert gas purge is 30 s.

[0117] Step 5: Annealing

[0118] The device was annealed in air at 200°C for 40 minutes.

[0119] Comparative Example 1

[0120] In this embodiment, only trimethylaluminum is used as the aluminum source for the aluminum oxide film, and the growth thickness is 5 nm.

[0121] The bottom-gate TFT selected has a channel layer length of 20 microns and a width of 50 microns, and the channel layer uses 4nm thick indium oxide.

[0122] Specific steps:

[0123] Step 1: Preheat the components of the atomic layer deposition equipment:

[0124] (1) Start the vacuum system of the atomic layer deposition equipment and evacuate the chamber;

[0125] (2) heating the atomic layer deposition chamber to 120°C; heating the trimethylaluminum precursor source bottle and pipeline to 30°C;

[0126] (3) After sufficient preheating, the prepared indium oxide thin film transistor sample is placed in the atomic layer deposition chamber and kept warm for 0.5 h.

[0127] Step 2: Growing aluminum oxide film

[0128] (1) Turn on the inert purge gas and adjust the chamber pressure to 400 mTorr;

[0129] (2) Opening the atomic layer deposition control program, performing 50 deposition cycles, and introducing trimethylaluminum-nitrogen purge gas-ozone-nitrogen purge gas in sequence in each cycle;

[0130] (3) The aluminum source pulse duration is 2 s, the inert gas purge is 25 s, the ozone pulse duration is 5 s, and the inert gas purge is 30 s.

[0131] Step 3: Annealing

[0132] The device was annealed in air at 200°C for 40 minutes.

[0133] Comparative Example 2

[0134] In this embodiment, tetrakis(ethylmethylamino)hafnium is used as the hafnium source of the hafnium oxide passivation film, and the growth thickness is 5 nm.

[0135] The bottom-gate TFT selected has a channel layer length of 20 microns and a width of 20 microns, and the channel layer uses 4nm thick indium oxide.

[0136] Specific steps:

[0137] Step 1: Preheat the components of the atomic layer deposition equipment:

[0138] (1) Start the vacuum system of the atomic layer deposition equipment and evacuate the chamber;

[0139] (2) heating the atomic layer deposition chamber to 120°C; heating the tetra(ethylmethylamino)hafnium precursor source bottle and pipeline to 80°C;

[0140] (3) After sufficient preheating, the prepared indium oxide thin film transistor sample is placed in the atomic layer deposition chamber and kept warm for 0.5 h.

[0141] Step 2: Growth of hafnium oxide passivation film

[0142] (1) Turn on the inert purge gas and adjust the chamber pressure to 400 mTorr;

[0143] (2) Opening the atomic layer deposition control program, performing 50 deposition cycles, and in each cycle, introducing tetrakis(ethylmethylamino)hafnium-nitrogen purge gas-ozone-nitrogen purge gas in sequence;

[0144] (3) The hafnium source pulse duration is 2 s, the inert gas purge is 25 s, the ozone pulse duration is 5 s, and the inert gas purge is 30 s.

[0145] Step 3: Annealing

[0146] The device was annealed in air at 200°C for 40 minutes.

[0147] Test results

[0148] The transfer characteristic curves of the bottom-gate thin film transistor before and after passivation in Example 1 are shown as follows: Figure 4 and 5 As shown. Figure 4 As shown, before passivation, the device switching ratio is 10 8 The field-effect mobility extracted from the linear region of the transfer curve is 16.8 cm 2 / V·s, the threshold voltage is -0.3V. Figure 5 As shown, after passivation, the field effect mobility of the transistor reaches 40.3 cm 2 / V·s, the device threshold voltage shifts negatively to -2.1V, and the device still exhibits a normal switching state, with the on / off ratio maintained at 10 8 , indicating that the transistor still maintains excellent switching performance after passivation.

[0149] The transfer characteristic curves of the bottom-gate thin film transistor before and after passivation in Example 2 are shown as follows: Figure 6 and 7 As shown. Figure 6 As shown, before passivation, the device switching ratio is 10 8 The field-effect mobility extracted from the linear region of the transfer curve is 20.7 cm 2 / V·s, the threshold voltage is -0.2V. Figure 7 As shown, after passivation, the field effect mobility of the transistor reaches 52.3 cm 2 / V·s, the device threshold voltage shifts negatively to -1.5V, and the device can still show normal switching state, and the switching ratio remains at 108 , indicating that the transistor still maintains excellent switching performance after passivation.

[0150] The transfer characteristic curves of the bottom-gate thin film transistor before and after passivation in Example 3 are shown as follows: Figure 8 and 9 As shown. Figure 8 As shown, before passivation, the device switching ratio is 10 7 The field-effect mobility extracted from the linear region of the transfer curve is 7.1 cm 2 / V·s, the threshold voltage is -0.5V. Figure 9 As shown, after passivation, the field effect mobility of the transistor reaches 13.5 cm 2 / V·s, the device threshold voltage shifts negatively to -1.1V, and the device still exhibits a normal switching state, with the on / off ratio maintained at 10 6 , indicating that the transistor still maintains excellent switching performance after passivation.

[0151] The transfer characteristic curves of the bottom-gate thin film transistor before and after passivation in Comparative Example 1 are shown as follows: Figure 10 and 11 As shown. Figure 10 As shown, before passivation, the device switching ratio is 10 7 The field-effect mobility extracted from the linear region of the transfer curve is 41.7 cm 2 / V·s, the threshold voltage is -0.6V. Figure 11 As shown in the figure, after passivation, under the condition of a gate voltage of -5V, the transistor still has a current of up to 1.4μA / μm and cannot present a normal off state, indicating that when trimethylaluminum is used as the aluminum source of the passivation layer, it will cause serious damage to the active layer of the transistor, resulting in the transistor being unable to turn off.

[0152] The transfer characteristic curves of the bottom-gate thin film transistor before and after passivation in Comparative Example 2 are shown as follows: Figure 12 and 13 As shown. Figure 12 As shown, before passivation, the device switching ratio is 10 7 The field-effect mobility extracted from the linear region of the transfer curve is 29.4 cm 2 / V·s, the threshold voltage is -0.3V. Figure 13 As shown, after passivation, the transistor switching ratio degrades to 10 2 At the same time, a large leakage current appeared, indicating that when tetra(ethylmethylamino)hafnium is used as the hafnium source of the passivation layer, it will cause damage to the transistor and seriously deteriorate the performance.

[0153] In summary, the embodiment of the present invention adopts a low-activity aluminum precursor source, such as tri(dimethylamino)aluminum or aluminum triisopropoxide, to grow an aluminum oxide film by an atomic layer deposition method. On the basis of the aluminum oxide film as the bottom passivation film, an outer passivation film can be further prepared to obtain a passivation film with a double-layer structure. By adopting a process of depositing an aluminum oxide film using a low-activity aluminum precursor source, damage to the channel layer is effectively avoided. At the same time, the double-layer passivation film constructed based on the aluminum oxide film provided by the present invention can effectively encapsulate the oxide thin film transistor, isolate the thin film transistor from the molecules in the atmosphere, enhance the stability of the channel layer, and have high controllability and operability.

[0154] It should be understood that the application of the present invention is not limited to the above examples. For those skilled in the art, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A method for preparing an aluminum oxide thin film for a thin film transistor, characterized in that: Including steps: (1) After the chamber of the atomic layer deposition system is evacuated, it is heated, and a thin film transistor is placed in the chamber to keep it warm; (2) heating an aluminum precursor source, wherein the aluminum precursor source is one of tris(dimethylamino)aluminum, aluminum triisopropoxide, triethoxyaluminum, tris(diethylamino)aluminum, aluminum tri-sec-butoxide, aluminum trichloride, tris(diisopropylamino)aluminum, triethylaluminum, and aluminum tri-sec-butoxide; (3) adjusting the chamber pressure, sequentially introducing the aluminum precursor source, the inert gas, the oxygen source, and the inert gas into the chamber to form a deposition cycle, and repeating the deposition cycle; (4) Annealing the thin film transistor processed in step (3) to obtain the aluminum oxide thin film on the thin film transistor.

2. The method for preparing an aluminum oxide thin film for a thin film transistor according to claim 1, wherein: In step (1), the temperature of the atomic layer deposition chamber is heated to 50-500°C.

3. The method for preparing an aluminum oxide thin film for a thin film transistor according to claim 1, wherein: In step (1), the thin film transistor includes a substrate, a gate electrode, a gate dielectric, a source electrode, a drain electrode and an oxide active layer, and the oxide active layer is selected from one of indium gallium zinc oxide, indium oxide, zinc oxide, gallium oxide, tin oxide, indium gallium oxide, indium zinc oxide, zinc gallium oxide, indium gallium tin oxide or indium tin zinc oxide; the thin film transistor is kept warm in the chamber for 30 seconds to 3 hours.

4. The method for preparing an aluminum oxide thin film for a thin film transistor according to claim 1, wherein: In step (2), the temperature at which the aluminum precursor source is heated is 25 to 180°C.

5. The method for preparing an aluminum oxide thin film for a thin film transistor according to claim 1, wherein: In step (3), the time for introducing the aluminum precursor source is 0.1 to 20 seconds, the time for introducing the oxygen source is 0.1 to 20 seconds, and the time for introducing the inert gas is 1 to 60 seconds; Wherein, the inert gas is high-purity nitrogen or high-purity argon; The oxygen source is one of ozone, water, oxygen, nitrous oxide, nitrogen dioxide, nitrogen tetroxide, fatty alcohol or oxygen plasma.

6. The method for preparing an aluminum oxide thin film for a thin film transistor according to claim 1, wherein: In step (3), the deposition cycle is repeated 5 to 1000 times, and the thickness of the aluminum oxide film is 0.5 to 100 nm.

7. The method for preparing an aluminum oxide thin film for a thin film transistor according to claim 1, wherein: In step (4), the annealing temperature is 100 to 500° C., and the annealing time is 0 to 240 minutes.

8. An aluminum oxide thin film for a thin film transistor, characterized in that: The aluminum oxide thin film is prepared by the method for preparing an aluminum oxide thin film for a thin film transistor according to any one of claims 1 to 7.

9. A double-layer passivation film, characterized in that: The double-layer passivation film comprises a bottom passivation film and an outer passivation film, wherein the bottom passivation film is the aluminum oxide thin film for thin film transistors according to claim 8, and the outer passivation film is prepared on the surface of the aluminum oxide thin film; Wherein, the outer passivation film is any one of an aluminum oxide film, a titanium oxide film, a hafnium oxide film, a yttrium oxide film, a silicon oxide film and a silicon nitride film.

10. The double-layer passivation film according to claim 9, characterized in that: The outer passivation film is prepared by adopting one of atomic layer deposition technology, plasma assisted atomic layer deposition technology, chemical vapor deposition technology and plasma enhanced chemical vapor deposition technology.

Images