Aluminum oxide / a-IGZO thin film transistor and preparation method thereof

Abstract

The present invention discloses an aluminum oxide / a-IGZO thin film transistor and a preparation method thereof. The preparation method ionizes oxygen introduced into a PLD cavity by a hollow cathode plasma discharge method to form a deposition environment with a high oxygen plasma concentration. + An aluminum oxide passivation layer is deposited on a α-Si substrate via pulsed laser deposition, followed by vacuum annealing to further optimize film performance. After furnace cooling to 20°C, a combination of hollow cathode oxygen plasma and vacuum in-situ annealing promotes the diffusion of mobile oxygen from the passivation layer into the a-IGZO channel layer, significantly reducing the oxygen vacancy content at the channel / passivation layer interface. This optimizes the device's subthreshold swing and mobility, ultimately improving gate voltage stability.

Description

Technical Field

[0001] The present invention belongs to the field of thin film transistors, and in particular relates to an aluminum oxide / a-IGZO thin film transistor and a preparation method thereof. Background Art

[0002] Thin-film transistors (TFTs) are crucial switching devices in flat-panel display technology. Amorphous metal oxide semiconductors, such as amorphous indium gallium zinc oxide (a-IGZO), are promising candidates for channel layer materials that could revolutionize next-generation large-scale, high-resolution, and high-response flexible display technologies. The stability of a TFT's gate voltage is crucial to the display's brightness and operating life. Previous studies have shown that depositing a passivation layer on the channel layer of an a-IGZO TFT can effectively improve the device's gate voltage stability.

[0003] Aluminum oxide (Al2O3) has good transmittance and insulation properties, is resistant to atmospheric reactions, and has a low production cost, making it an ideal material for thin-film transistor passivation layers. However, commonly prepared aluminum oxide passivation layers contain a high number of oxygen defects, which can severely affect the device's electrical performance. Summary of the Invention

[0004] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide an aluminum oxide / a-IGZO thin film transistor and a preparation method thereof to solve the problem of many oxygen defects in the aluminum oxide passivation layer on the a-IGZO thin film.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for preparing an aluminum oxide / a-IGZO thin film transistor comprises the following steps:

[0007] Step 1: Patterned a-IGZO / SiO2 / P + -Si is placed in a PLD chamber, heated to 100°C to 220°C under vacuum conditions, kept at this temperature for 3 to 12 hours for the first annealing, and then cooled to obtain a first process sample;

[0008] Step 2: The first process sample is placed in a PLD chamber, using alumina ceramic as a target. Oxygen is introduced into the PLD chamber through a hollow metal tube. The PLD chamber is grounded, and the hollow metal tube serves as a cathode. A high-voltage DC power supply applies an ionization voltage to the cathode. The alumina ceramic target is sputtered by a KrF laser to deposit an Al2O3 thin film on the a-IGZO of the first process sample, thereby obtaining a second process sample.

[0009] Step 3, removing the photoresist on the surface of the second process, preparing source and drain electrodes on the second process sample, and obtaining a third process sample;

[0010] Step 4: anneal the sample from the third process for a second time at 80° C. to 140° C. under vacuum conditions for 3 to 12 hours, and obtain an aluminum oxide / a-IGZO thin film transistor after cooling.

[0011] A further improvement of the present invention is:

[0012] Preferably, in step 1, the vacuum pressure is ≤5×10 - 5Pa.

[0013] Preferably, in step 2, before oxygen is filled, the PLD chamber is vacuumed to a degree of vacuum ≤ 5×10 -5 Pa.

[0014] Preferably, in step 2, the oxygen partial pressure after oxygen is filled is 4.5-6.0 Pa.

[0015] Preferably, in step 2, the ionization voltage is 0.5-3.0 kV; the frequency of KrF laser sputtering is 1-10 Hz, and the laser power is 200-600 mJ.

[0016] Preferably, in step 2, the thickness of the Al2O3 film is 60 to 100 nm.

[0017] Preferably, in step 3, the source and drain electrodes are made of Mo, and the thickness of the source and drain electrodes is 100 nm.

[0018] Preferably, in step 4, the vacuum condition of the third process sample is a vacuum degree ≤ 5×10 -5 Pah.

[0019] Preferably, in step 1, the patterned a-IGZO / SiO2 / P + -Si preparation process is: SiO2 / P + -Si substrate is fixed in the PLD chamber, and the vacuum degree of the PLD chamber is pumped to ≤5×10 -5 Pa, 3.2~3.7Pa of oxygen was filled into the PLD cavity; KrF laser was used at 10Jcm -2 Laser energy per pulse, repetition rate of 1-10Hz, laser power of 200-600mJ, in SiO2 / P + -Si substrate and deposited 20 to 40 nm thick a-IGZO thin film.

[0020] An aluminum oxide / a-IGZO thin film transistor prepared by any one of the preparation methods described above, wherein aluminum oxide is deposited on the a-IGZO thin film in the thin film transistor as a passivation layer.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention discloses a method for preparing an aluminum oxide / a-IGZO thin film transistor. The method is a method for preparing a high-quality aluminum oxide passivation layer on an a-IGZO thin film transistor (a-IGZO TFT). + The a-IGZO thin film sample grown on a -Si substrate is placed in a pulsed laser deposition (PLD) chamber, evacuated for the first annealing treatment, and then cooled to room temperature in a high vacuum environment. Under the conditions of hollow cathode oxygen plasma discharge, the aluminum oxide passivation layer is prepared in situ using PLD at low temperature, and then the a-IGZO / Al2O3 composite film is subjected to a second vacuum annealing and cooled to room temperature in nitrogen. This preparation method uses the hollow cathode plasma discharge method to ionize the oxygen introduced into the PLD chamber to form a deposition environment with a high oxygen plasma concentration. + -Si substrate by pulsed laser deposition to prepare an aluminum oxide passivation layer, and then vacuum annealing is performed to further optimize the film performance. After cooling to 20°C with the furnace, hollow cathode oxygen plasma and vacuum in-situ annealing are combined to promote the diffusion of movable oxygen in the passivation layer to the a-IGZO channel layer, significantly reducing the oxygen vacancy content at the channel layer / passivation layer interface, optimizing the subthreshold swing and mobility of the device, and helping to improve the gate voltage stability of the device. In the pulsed laser deposition (PLD) process, oxygen is introduced into the cavity through a metal tube, which reduces the oxygen defect concentration compared to the existing direct introduction of oxygen. The performance of the prepared aluminum oxide film as a passivation layer device is better than that of the existing passivation layer device prepared by directly introducing oxygen, and the oxygen defect concentration is reduced. The present invention adopts hollow cathode plasma discharge to assist PLD deposition and combines it with a two-step vacuum annealing process to achieve the preparation of a high-quality aluminum oxide passivation layer for thin film transistors.

[0023] The present invention also discloses an aluminum oxide / a-IGZO thin film transistor, which exhibits good electronic performance and a mobility of up to 22.8 cm 2 V -1 s -1 , subthreshold swing is 0.6Vdecade -1 , the on / off ratio is 6.3×10 6 , the threshold voltage drift is 5.7V, and the overall performance is excellent. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The transfer characteristic curve of the a-IGZO TFT device prepared in Example 1 of the present invention is shown; the solid line and the dotted line represent the curves before and after drift, respectively.

[0025] Figure 2 Transfer characteristic curves of a-IGZO TFT devices prepared in Comparative Example 1, Comparative Example 2, and Comparative Example 3;

[0026] (a) Transfer characteristic curves of Comparative Example 1 (b) Comparative Example 2 (c) Comparative Example 3, where the solid line and dotted line represent the curves before and after drift, respectively.

[0027] Figure 3 The transfer characteristic curves of the a-IGZO TFT devices prepared in Example 2 and Comparative Examples 4 and 5 of the present invention are shown.

[0028] Transfer curves of (a) Example 2, (b) Comparative Example 4, and (c) Comparative Example 5. DETAILED DESCRIPTION

[0029] The present invention is described in further detail below with reference to the accompanying drawings:

[0030] The present invention discloses a method for preparing an aluminum oxide / a-IGZO thin film transistor, which comprises the following steps:

[0031] Step 1, SiO2 / P + -Si substrate is fixed on the PLD sample holder, the target-substrate distance is controlled to 50-70mm, and the vacuum pump system is used to evacuate the cavity to a PLD vacuum degree of ≤5×10 -5 Pa, 3.2~3.7Pa of 99.999% pure oxygen was filled into the cavity. KrF excimer laser was used at 10Jcm -2 The laser energy per pulse, repetition rate of 1 to 10 Hz, and laser power of 200 to 600 mJ are used to deposit a 20 to 40 nm thick a-IGZO film. After deposition, the a-IGZO film is patterned using photolithography to remove excess material, leaving photoresist at the electrode locations and defining the channel length and width.

[0032] Step 2: Patterned a-IGZO / SiO2 / P + -Si was placed into the PLD cavity again and the 5×10 -5 Under a vacuum environment of 100°C (Pa), the temperature is raised to 100°C to 220°C at a rate of 20-40°C / min, held for 3-12 hours, and then cooled to 20°C in the furnace. During the cooling process, the PLD chamber is maintained at a high vacuum to prevent the prepared sample from coming into contact with oxygen, resulting in the first-stage sample. This annealing process removes weakly bound oxygen from the a-IGZO film, thereby eliminating deep-level defect states, improving field-effect mobility and suppressing threshold voltage drift. After annealing, aluminum oxide is deposited in situ in a vacuum, effectively reducing oxygen contact between the a-IGZO and oxygen, preventing oxygen diffusion into the a-IGZO, and minimizing oxygen-induced threshold voltage drift and mobility degradation.

[0033] Step 3: In the first process, the sample is always in the PLD cavity. The alumina ceramic target is fixed on the PLD target holder. The target-substrate distance is controlled to be 50-70 mm. The vacuum degree of the cavity is pumped to better than 5×10 -5 Pa. In order to increase the reactivity of oxygen and make up for the oxygen vacancies in alumina, oxygen is ionized into oxygen plasma. In the actual PLD device, the hollow cathode discharge method is selected to provide oxygen plasma. The specific process is: use a hollow metal tube with an inner diameter of 3mm-6mm to fill the cavity with 4.5-6.0Pa of 99.999% pure oxygen, and use the hollow metal tube as the cathode. The cavity is grounded and a high-voltage DC power supply is used to apply an ionization voltage of 0.5-3.0kV to the cathode to generate oxygen plasma. The hollow cathode combines with the oxygen plasma and the oxygen in the IGZO. A KrF laser is used at 10Jcm -2 A 60–100 nm thick Al2O3 film was deposited using a laser energy of 100 nm, a repetition rate of 1–10 Hz, and a laser power of 200–600 mJ. After deposition, the film was removed and used for later use, yielding the second-stage sample. The Al2O3 film serves as a passivation layer between the air and the IGZO film. Too thin an Al2O3 film prevents air from penetrating into the IGZO film, while too thick a thickness results in high production costs. Al2O3 films with a thickness of 60–100 nm effectively block air. The oxygen partial pressure during the deposition ionization process ranges from 1.0 to 6.0 Pa. Lower oxygen partial pressures increase the oxygen vacancy concentration in the alumina film. The oxygen atoms in a-IGZO have a weaker bond with indium atoms than with aluminum atoms in alumina. Consequently, oxygen atoms in the a-IGZO migrate into the alumina at the interface, increasing the oxygen vacancy concentration in the a-IGZO at the interface. Oxygen vacancies in a-IGZO act as electron donors, and their increased concentration leads to poor subthreshold performance in the device. When the deposited oxygen partial pressure increases, the concentration of unstable oxygen atoms in the aluminum oxide increases. When these oxygen atoms diffuse into the a-IGZO, the concentration of weakly bound oxygen atoms in the a-IGZO increases. These weakly bound oxygen atoms will generate deep energy level defects, which in turn generate bound electrons, causing a significant shift in the threshold voltage and a decrease in field-effect mobility.

[0034] Step 4: Remove the photoresist from the second-stage sample and use photolithography to define the source and drain locations of the transistor. Deposit 100nm of Mo as the source and drain electrodes using RF magnetron sputtering. After deposition, remove the photoresist from the sample to obtain a complete thin-film transistor, which is the third-stage sample.

[0035] Step 5, second annealing, the prepared third process sample is placed in the high vacuum PLD chamber again, and the vacuum degree is less than or equal to 5×10 -5Under the conditions of 100 Pa, the sample was heated to 80°C-140°C at a rate of 20-40°C / min, held at this temperature for 3-12 hours, and then cooled to 20°C in nitrogen at a rate of 20-40°C / min to prevent oxidation during the cooling process. During the deposition process, oxygen atoms inevitably diffuse from the a-IGZO into the a-IGZO at the interface between the alumina and a-IGZO, increasing the concentration of oxygen vacancies in the a-IGZO at the interface and deteriorating the subthreshold characteristics. During the second annealing, unstable oxygen atoms in the Al2O3 diffuse into the interface, reducing the oxygen vacancy concentration in the a-IGZO. This shifted the turn-on voltage positively, improving the subthreshold characteristics. Since the concentration of weakly bound oxygen atoms on the a-IGZO surface inevitably increases during this process, strict control of the annealing temperature is required to suppress the threshold voltage drift and mobility degradation.

[0036] In the present invention, oxygen ion vacancies can be formed inside the a-IGZO film through the first annealing, thereby increasing the oxygen vacancy concentration and eliminating deep energy level defect states; and the oxygen vacancy defects at the interface between the two phases can be eliminated through the second annealing.

[0037] The prepared thin film transistor is composed of a patterned Mo electrode, a patterned aluminum oxide passivation layer, a patterned a-IGZO, and a SiO2 / P + -Si substrate

[0038] The following describes the details in conjunction with specific embodiments.

[0039] Example 1

[0040] This embodiment provides a method for preparing an aluminum oxide / a-IGZO thin film transistor, which includes the following steps:

[0041] (1) The SiO2 / P+-Si substrate was fixed on the PLD sample holder, the target-substrate distance was controlled to 70 mm, and the vacuum pump system was used to evacuate the cavity to a vacuum degree of less than 5×10 -5 Pa, 3.2Pa of 99.999% pure oxygen was filled into the cavity. A KrF excimer laser was used with a power of 10Jcm -2 With a laser energy per pulse, a repetition rate of 2Hz, and a laser power of 400mJ, a 20nm thick a-IGZO film was deposited. The prepared a-IGZO film was patterned using photolithography, removing excess material while retaining photoresist at the electrode locations to determine the channel length and width.

[0042] (2) Patterned a-IGZO / SiO2 / P + -Si was placed in the PLD cavity again, heated to 220°C at a rate of 30°C / min, kept at this temperature for 3 h, and cooled to 20°C with the furnace. During this period, the high vacuum in the PLD cavity was kept unchanged.

[0043] (3) Fix the alumina ceramic target on the PLD target holder, control the target-base distance to be 50 mm, and use the vacuum pump system to evacuate the cavity to a vacuum degree of less than 5×10 -5 Pa. A hollow metal tube with an inner diameter of 3 mm was used to fill the cavity with 6.0 Pa of 99.999% pure oxygen. The hollow metal tube was used as the cathode, the cavity was grounded, and a high-voltage DC power supply was used to apply an ionization voltage of 1.5 kV to the cathode to generate oxygen plasma. A KrF laser was used at 10 J cm -2 With a laser energy of 1000 mJ per pulse, a repetition rate of 2 Hz, and a laser power of 400 mJ, a 60 nm thick Al2O3 film was deposited. After deposition, the film was removed from the chamber.

[0044] (4) Remove the photoresist from the sample surface and use photolithography again to define the source and drain locations of the transistor. Use radio frequency magnetron sputtering to deposit 100nm of Mo as the source and drain electrodes. After deposition, remove the photoresist from the sample surface to obtain a complete thin film transistor.

[0045] (5) The prepared thin film transistor was placed in a high vacuum PLD chamber again, and the sample was heated to 140°C at a rate of 30°C / min, kept at this temperature for 3 h, and cooled to 20°C in nitrogen at a rate of 30°C / min.

[0046] Comparative Example 1

[0047] The difference between Comparative Example 1 and Example 1 is that no annealing treatment is performed on the a-IGZO film and the Al2O3 / a-IGZO film, and the other steps and parameters are the same as those in Example 1.

[0048] Comparative Example 2

[0049] The difference between Comparative Example 2 and Example 1 is that only the a-IGZO thin film is annealed, and the other steps and parameters are the same as those in Example 1.

[0050] Comparative Example 3

[0051] The difference between Comparative Example 3 and Example 1 is that only the a-IGZO film after Al2O3 passivation is annealed, and the other steps and parameters are the same as those in Example 1.

[0052] The transfer characteristic curves of the Al2O3 / a-IGZO TFT thin film transistors prepared in Example 1 and Comparative Examples 1, 2 and 3 are shown in FIG. Figure 1 and Figure 2 The performance parameters are shown in Table 1.

[0053] Table 1: Transistor performance parameters of Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3

[0054] Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 <![CDATA[Mobility / cm 2 V -1 s -1 ]]> 8.55 10.00 19.28 2.2 lg (on-off radio) 4.13 6.11 0.32 3.80 <![CDATA[SS / Vdecade -1 ]]> 1.5 0.47 / 0.46 <![CDATA[ΔV th / V]]> 5.75 9.88 3.34 26

[0055] Combined with Table 1, Figure 1 and Figure 2 From the transfer characteristic curve, it can be seen that the turn-on voltage of the Al2O3 / a-IGZO film after annealing is close to 0V, the on-off ratio is high, but the field effect mobility is reduced and the threshold voltage drift is increased; while annealing only the a-IGZO film is beneficial to improving the field effect mobility of the device and suppressing the threshold voltage drift of the device, but the subthreshold performance of the device is very poor and is in a fully on state with a low on-off ratio, which is related to the high concentration of carriers generated.

[0056] Example 2

[0057] This embodiment provides a method for preparing an aluminum oxide / a-IGZO thin film transistor, which includes the following steps:

[0058] (1) SiO2 / P + -Si substrate is fixed on the PLD sample holder, the target-substrate distance is controlled to 70mm, and the vacuum pump system is used to evacuate the cavity to a vacuum degree better than 5×10 -5 Pa, 3.7 Pa of 99.999% pure oxygen was filled into the cavity. A KrF excimer laser was used with a power of 10 J cm -2 With a laser energy per pulse, a repetition rate of 2Hz, and a laser power of 400mJ, a 40nm thick a-IGZO film was deposited. The prepared a-IGZO film was patterned using photolithography, removing excess material while retaining photoresist at the electrode locations to determine the channel length and width.

[0059] (2) Patterned a-IGZO / SiO2 / P + -Si was placed in the PLD cavity again, and the sample was heated to 180°C at a rate of 30°C / min, kept at this temperature for 3 h, and cooled to 20°C with the furnace. During this period, the high vacuum in the PLD cavity was kept unchanged.

[0060] (3) Fix the alumina ceramic target on the PLD target holder, control the target-base distance to be 50 mm, and use the vacuum pump system to evacuate the cavity to a vacuum degree better than 5×10 -5 Pa. A hollow metal tube with an inner diameter of 6 mm was used to fill the cavity with 6.0 Pa of 99.999% pure oxygen. The hollow metal tube was used as the cathode, the cavity was grounded, and a high-voltage DC power supply was used to apply an ionization voltage of 1.5 kV to the cathode to generate oxygen plasma in the cavity. A KrF laser was used at 10 J cm -2With a laser energy of 100 mJ per pulse, a repetition rate of 2 Hz, and a laser power of 400 mJ, a 100 nm thick Al2O3 film was deposited. After deposition, the film was removed from the chamber.

[0061] (4) Remove the photoresist from the sample surface and use photolithography to define the source and drain locations of the transistor. Use radio frequency magnetron sputtering to deposit 100nm of Mo as the source and drain electrodes. After deposition, remove the photoresist from the sample surface to obtain a complete thin film transistor.

[0062] (5) The prepared thin film transistor was placed in a high vacuum PLD chamber again, and the sample was heated to 100°C at a rate of 30°C / min, kept at this temperature for 3 h, and cooled to 20°C in nitrogen at a rate of 30°C / min.

[0063] Comparative Example 4

[0064] The difference between this comparative example 4 and Example 2 is that the hollow cathode discharge plasma is not turned on and the a-IGZO film and the Al2O3 / a-IGZO film are not annealed. The other steps and parameters are the same as those in Example 2.

[0065] Comparative Example 5

[0066] The only difference between Comparative Example 5 and Example 2 is that no annealing treatment is performed on the a-IGZO film and the Al2O3 / a-IGZO film. Other steps and parameters are the same as those in Example 2.

[0067] The transfer curves of Al2O3 / a-IGZO TFTs prepared in Example 2, Comparative Example 4 and Comparative Example 5 are shown in FIG. Figure 3 The transistor performance parameters are shown in Table 2.

[0068] Table 2: Transistor performance parameters of Example 2, Comparative Example 4, and Comparative Example 5

[0069] Example 2 Comparative Example 4 Comparative Example 5 <![CDATA[Mobility / cm 2 V -1 s -1 ]]> 22.79 4.5 8.1 lg (on-off radio) 7.60 1.71 5.11 <![CDATA[SS / Vdecade -1 ]]> 0.6 2.0 0.76

[0070] Combined with Table 2, Figure 3 The transfer characteristic curve shows that when hollow cathode plasma is not used for assisting, the subthreshold characteristics of the device are poor, the device is in a normally open state, and the turn-on voltage is about -20V, which increases the operating power consumption. The mobility of the Al2O3 / a-IGZO TFT device prepared using hollow cathode plasma assisted PLD is 8.1cm 2 V -1 s -1 , subthreshold swing is 0.76Vdecade -1 , the on / off ratio is 1.3×10 5, the turn-on voltage is close to 0V, and the performance of the device is significantly improved. It can be seen that when a hollow cathode is used to prepare the aluminum oxide passivation layer, combined with the 180℃ annealing process of the a-IGZO film and the 100℃ annealing process of the Al2O3 / a-IGZO device, the device performance can be optimized, and its mobility is as high as 22.8cm 2 V -1 s -1 , subthreshold swing is 0.6Vdecade -1 , the on / off ratio is 6.3×10 6 , the threshold voltage drift is 5.7V.

[0071] Example 3

[0072] This embodiment provides a method for preparing an aluminum oxide / a-IGZO thin film transistor, which includes the following steps:

[0073] (1) SiO2 / P + -Si substrate is fixed on the PLD sample holder, the target-substrate distance is controlled to 50mm, and the vacuum pump system is used to evacuate the cavity to a vacuum degree better than 5×10 -5 Pa, 3.3 Pa of 99.999% pure oxygen was filled into the cavity. A KrF excimer laser was used with a power of 10 J cm -2 With a laser energy per pulse, a repetition rate of 1Hz, and a laser power of 600mJ, a 25nm thick a-IGZO film was deposited. The prepared a-IGZO film was patterned using photolithography, removing excess material while retaining photoresist at the electrode locations to determine the channel length and width.

[0074] (2) Patterned a-IGZO / SiO2 / P + -Si was placed in the PLD chamber again, and the sample was heated to 200°C at a rate of 20°C / min, kept at this temperature for 5 h, and cooled to 20°C with the furnace. During this period, the high vacuum in the PLD chamber was kept unchanged.

[0075] (3) Fix the alumina ceramic target on the PLD target holder, control the target-base distance to be 50 mm, and use the vacuum pump system to evacuate the cavity to a vacuum degree better than 5×10 -5 Pa. A hollow metal tube with an inner diameter of 4 mm was used to fill the cavity with 4.5 Pa of 99.999% pure oxygen. The hollow metal tube was used as the cathode, the cavity was grounded, and a high-voltage DC power supply was used to apply an ionization voltage of 1.5 kV to the cathode to generate oxygen plasma in the cavity. A KrF laser was used at 10 J cm -2 With a laser energy of 1000 mJ per pulse, a repetition rate of 1 Hz, and a laser power of 600 mJ, a 70 nm thick Al2O3 film was deposited. After deposition, the film was removed from the chamber.

[0076] (4) Remove the photoresist from the sample surface and use photolithography to define the source and drain locations of the transistor. Use radio frequency magnetron sputtering to deposit 100nm of Mo as the source and drain electrodes. After deposition, remove the photoresist from the sample surface to obtain a complete thin film transistor.

[0077] (5) The prepared thin film transistor was placed in a high vacuum PLD chamber again, and the sample was heated to 80°C at a rate of 20°C / min, kept at this temperature for 4 h, and cooled to 20°C in nitrogen at a rate of 20°C / min.

[0078] Example 4

[0079] This embodiment provides a method for preparing an aluminum oxide / a-IGZO thin film transistor, which includes the following steps:

[0080] (1) SiO2 / P + -Si substrate is fixed on the PLD sample holder, the target-substrate distance is controlled to 55mm, and the vacuum pump system is used to evacuate the cavity to a vacuum degree better than 5×10 -5 Pa, 3.4 Pa of 99.999% pure oxygen was filled into the cavity. A KrF excimer laser was used with a power of 10 J cm -2 With a laser energy per pulse, a repetition rate of 3Hz, and a laser power of 300mJ, a 30nm thick a-IGZO film was deposited. The prepared a-IGZO film was patterned using photolithography, removing excess material while retaining photoresist at the electrode locations to determine the channel length and width.

[0081] (2) Patterned a-IGZO / SiO2 / P + -Si was placed in the PLD cavity again, and the sample was heated to 150 °C at a rate of 25 °C / min, kept at this temperature for 7 h, and cooled to 20 °C with the furnace. During this period, the high vacuum in the PLD cavity was kept unchanged.

[0082] (3) Fix the alumina ceramic target on the PLD target holder, control the target-base distance to be 55 mm, and use the vacuum pump system to evacuate the cavity to a vacuum degree better than 5×10 -5 Pa. A hollow metal tube with an inner diameter of 4 mm was used to fill the cavity with 4.8 Pa of 99.999% pure oxygen. The hollow metal tube was used as the cathode, the cavity was grounded, and a high-voltage DC power supply was used to apply an ionization voltage of 0.5 kV to the cathode to generate oxygen plasma in the cavity. A KrF laser was used at 10 J cm -2 With a laser energy of 1000 mJ per pulse, a repetition rate of 3 Hz, and a laser power of 300 mJ, an 80 nm thick Al2O3 film was deposited. After deposition, the film was removed from the chamber.

[0083] (4) Remove the photoresist from the sample surface and use photolithography to define the source and drain locations of the transistor. Use radio frequency magnetron sputtering to deposit 100nm of Mo as the source and drain electrodes. After deposition, remove the photoresist from the sample surface to obtain a complete thin film transistor.

[0084] (5) The prepared thin film transistor was placed in a high vacuum PLD chamber again, and the sample was heated to 130°C at a rate of 20°C / min, kept at this temperature for 5 h, and cooled to 20°C in nitrogen at a rate of 20°C / min.

[0085] Example 5

[0086] This embodiment provides a method for preparing an aluminum oxide / a-IGZO thin film transistor, which includes the following steps:

[0087] (1) SiO2 / P + -Si substrate is fixed on the PLD sample holder, the target-substrate distance is controlled to 60mm, and the vacuum pump system is used to evacuate the cavity to a vacuum degree better than 5×10 -5 Pa, 5Pa of 99.999% pure oxygen was filled into the cavity. A KrF excimer laser was used with a power of 10Jcm -2 With a laser energy of 400 mJ per pulse, a repetition rate of 5 Hz, and a laser power of 500 mJ, a 35 nm thick a-IGZO film was deposited. The prepared a-IGZO film was patterned using photolithography, removing excess material while retaining photoresist at the electrode locations to determine the channel length and width.

[0088] (2) Patterned a-IGZO / SiO2 / P + -Si was placed in the PLD cavity again, and the sample was heated to 160°C at a rate of 30°C / min, kept at this temperature for 6 h, and cooled to 20°C with the furnace. During this period, the high vacuum in the PLD cavity was kept unchanged.

[0089] (3) Fix the alumina ceramic target on the PLD target holder, control the target-base distance to 60 mm, and use the vacuum pump system to evacuate the cavity to a vacuum degree better than 5×10 -5 Pa. A hollow metal tube with an inner diameter of 4 mm was used to fill the cavity with 2 Pa of 99.999% pure oxygen. The hollow metal tube was used as the cathode, the cavity was grounded, and a high-voltage DC power supply was used to apply an ionization voltage of 1 kV to the cathode to generate oxygen plasma in the cavity. A KrF laser was used at 10 J cm -2 With a laser energy of 1000 mJ per pulse, a repetition rate of 5 Hz, and a laser power of 400 mJ, a 90 nm thick Al2O3 film was deposited. After deposition, the film was removed from the chamber.

[0090] (4) Remove the photoresist from the sample surface and use photolithography to define the source and drain locations of the transistor. Use radio frequency magnetron sputtering to deposit 100nm of Mo as the source and drain electrodes. After deposition, remove the photoresist from the sample surface to obtain a complete thin film transistor.

[0091] (5) The prepared thin film transistor was placed in a high vacuum PLD chamber again, and the sample was heated to 120°C at a rate of 40°C / min, kept at this temperature for 6 h, and cooled to 20°C in nitrogen at a rate of 25°C / min.

[0092] Example 6

[0093] This embodiment provides a method for preparing an aluminum oxide / a-IGZO thin film transistor, which includes the following steps:

[0094] (1) SiO2 / P + -Si substrate is fixed on the PLD sample holder, the target-substrate distance is controlled to 65mm, and the vacuum pump system is used to evacuate the cavity to a vacuum degree better than 5×10 -5 Pa, 3.6 Pa of 99.999% pure oxygen was filled into the cavity. A KrF excimer laser was used with a power of 10 J cm -2 With a laser energy per pulse, a repetition rate of 6 Hz, and a laser power of 500 mJ, a 40 nm thick a-IGZO film was deposited. The prepared a-IGZO film was patterned using photolithography, removing excess material while retaining photoresist at the electrode locations to determine the channel length and width.

[0095] (2) Patterned a-IGZO / SiO2 / P + -Si was placed in the PLD cavity again, and the sample was heated to 140 °C at a rate of 35 °C / min, kept at this temperature for 8 h, and cooled to 20 °C with the furnace. During this period, the high vacuum in the PLD cavity was kept unchanged.

[0096] (3) Fix the alumina ceramic target on the PLD target holder, control the target-base distance to be 65 mm, and use the vacuum pump system to evacuate the cavity to a vacuum degree better than 5×10 -5 Pa. A hollow metal tube with an inner diameter of 5 mm was used to fill the cavity with 4.5 Pa of 99.999% pure oxygen. The hollow metal tube was used as the cathode, the cavity was grounded, and a high-voltage DC power supply was used to apply an ionization voltage of 3 kV to the cathode to generate oxygen plasma in the cavity. A KrF laser was used at 10 J cm -2 With a laser energy of 500 mJ per pulse, a repetition rate of 6 Hz, and a laser power of 500 mJ, a 75 nm thick Al2O3 film was deposited. After deposition, the film was removed from the chamber.

[0097] (4) Remove the photoresist from the sample surface and use photolithography to define the source and drain locations of the transistor. Use radio frequency magnetron sputtering to deposit 100nm of Mo as the source and drain electrodes. After deposition, remove the photoresist from the sample surface to obtain a complete thin film transistor.

[0098] (5) The prepared thin film transistor was placed in a high vacuum PLD chamber again, and the sample was heated to 110°C at a rate of 40°C / min, kept at this temperature for 8 h, and cooled to 20°C in nitrogen at a rate of 35°C / min.

[0099] Example 7

[0100] This embodiment provides a method for preparing an aluminum oxide / a-IGZO thin film transistor, which includes the following steps:

[0101] (1) SiO2 / P + -Si substrate is fixed on the PLD sample holder, the target-substrate distance is controlled to 70mm, and the vacuum pump system is used to evacuate the cavity to a vacuum degree better than 5×10 -5 Pa, 3.3 Pa of 99.999% pure oxygen was filled into the cavity. A KrF excimer laser was used with a power of 10 J cm -2 With a laser energy per pulse, an 8Hz repetition rate, and a laser power of 250mJ, a 30nm thick a-IGZO film was deposited. The prepared a-IGZO film was patterned using photolithography, removing excess material while retaining photoresist at the electrode locations to determine the channel length and width.

[0102] (2) Patterned a-IGZO / SiO2 / P + -Si was placed in the PLD cavity again, and the sample was heated to 130°C at a rate of 40°C / min, kept at this temperature for 10 h, and cooled to 20°C with the furnace. During this period, the high vacuum in the PLD cavity was kept unchanged.

[0103] (3) Fix the alumina ceramic target on the PLD target holder, control the target-base distance to 70 mm, and use the vacuum pump system to evacuate the cavity to a vacuum degree better than 5×10 -5 Pa. A hollow metal tube with an inner diameter of 5 mm was used to fill the cavity with 5.5 Pa of 99.999% pure oxygen. The hollow metal tube was used as the cathode, the cavity was grounded, and a high-voltage DC power supply was used to apply an ionization voltage of 1.5 kV to the cathode to generate oxygen plasma in the cavity. A KrF laser was used at 10 J cm -2 With a laser energy per pulse, a repetition rate of 8 Hz, and a laser power of 250 mJ, an 85 nm thick Al2O3 film was deposited. After deposition, the film was removed from the chamber.

[0104] (4) Remove the photoresist from the sample surface and use photolithography to define the source and drain locations of the transistor. Use radio frequency magnetron sputtering to deposit 100nm of Mo as the source and drain electrodes. After deposition, remove the photoresist from the sample surface to obtain a complete thin film transistor.

[0105] (5) The prepared thin film transistor was placed in a high vacuum PLD chamber again, and the sample was heated to 100°C at a rate of 25°C / min, kept at this temperature for 10 h, and cooled to 20°C in nitrogen at a rate of 35°C / min.

[0106] Example 8

[0107] This embodiment provides a method for preparing an aluminum oxide / a-IGZO thin film transistor, which includes the following steps:

[0108] (1) SiO2 / P + -Si substrate is fixed on the PLD sample holder, the target-substrate distance is controlled to 52mm, and the vacuum pump system is used to evacuate the cavity to a vacuum degree better than 5×10 -5 Pa, 3.4 Pa of 99.999% pure oxygen was filled into the cavity. A KrF excimer laser was used with a power of 10 J cm -2 With a laser energy per pulse, a repetition rate of 10 Hz, and a laser power of 200 mJ, a 40 nm thick a-IGZO film was deposited. The prepared a-IGZO film was patterned using photolithography, removing excess material while retaining photoresist at the electrode locations to determine the channel length and width.

[0109] (2) Patterned a-IGZO / SiO2 / P + -Si was placed in the PLD cavity again, and the sample was heated to 120 °C at a rate of 25 °C / min, kept at this temperature for 5 h, and cooled to 20 °C with the furnace. During this period, the high vacuum in the PLD cavity was kept unchanged.

[0110] (3) Fix the alumina ceramic target on the PLD target holder, control the target-base distance to 52 mm, and use the vacuum pump system to evacuate the cavity to a vacuum degree better than 5×10 -5 Pa. A hollow metal tube with an inner diameter of 5 mm was used to fill the cavity with 5.2 Pa of 99.999% pure oxygen. The hollow metal tube was used as the cathode, the cavity was grounded, and a high-voltage DC power supply was used to apply an ionization voltage of 1.8 kV to the cathode to generate oxygen plasma in the cavity. A KrF laser was used at 10 J cm -2 With a laser energy of 100 mJ per pulse, a repetition rate of 10 Hz, and a laser power of 200 mJ, a 100 nm thick Al2O3 film was deposited. After deposition, the film was removed from the chamber.

[0111] (4) Remove the photoresist from the sample surface and use photolithography to define the source and drain locations of the transistor. Use radio frequency magnetron sputtering to deposit 100nm of Mo as the source and drain electrodes. After deposition, remove the photoresist from the sample surface to obtain a complete thin film transistor.

[0112] (5) The prepared thin film transistor was placed in a high vacuum PLD chamber again, and the sample was heated to 90°C at a rate of 25°C / min, kept at this temperature for 12 h, and cooled to 20°C in nitrogen at a rate of 40°C / min.

[0113] Example 9

[0114] This embodiment provides a method for preparing an aluminum oxide / a-IGZO thin film transistor, which includes the following steps:

[0115] (1) SiO2 / P + -Si substrate is fixed on the PLD sample holder, the target-substrate distance is controlled to 58mm, and the vacuum pump system is used to evacuate the cavity to a vacuum degree better than 5×10 -5 Pa, 3.5Pa of 99.999% pure oxygen was filled into the cavity. A KrF excimer laser was used with a power of 10Jcm -2 With a laser energy per pulse, a repetition rate of 2Hz, and a laser power of 550mJ, a 25nm thick a-IGZO film was deposited. The prepared a-IGZO film was patterned using photolithography, removing excess material while retaining photoresist at the electrode locations to determine the channel length and width.

[0116] (2) Patterned a-IGZO / SiO2 / P + -Si was placed in the PLD chamber again, and the sample was heated to 100°C at a rate of 30°C / min, kept warm for 12 h, and cooled to 20°C with the furnace. During this period, the high vacuum in the PLD chamber was kept unchanged.

[0117] (3) Fix the alumina ceramic target on the PLD target holder, control the target-base distance to 58 mm, and use the vacuum pump system to evacuate the cavity to a vacuum degree better than 5×10 -5 Pa. A hollow metal tube with an inner diameter of 3 mm was used to fill the cavity with 5.8 Pa of 99.999% pure oxygen. The hollow metal tube was used as the cathode, the cavity was grounded, and a high-voltage DC power supply was used to apply an ionization voltage of 2 kV to the cathode to generate oxygen plasma in the cavity. A KrF laser was used at 10 J cm -2 With a laser energy of 500 mJ per pulse, a repetition rate of 2 Hz, and a laser power of 550 mJ, a 75 nm thick Al2O3 film was deposited. After deposition, the film was removed from the chamber.

[0118] (4) Remove the photoresist from the sample surface and use photolithography to define the source and drain locations of the transistor. Use radio frequency magnetron sputtering to deposit 100nm of Mo as the source and drain electrodes. After deposition, remove the photoresist from the sample surface to obtain a complete thin film transistor.

[0119] (5) The prepared thin film transistor was placed in a high vacuum PLD chamber again, and the sample was heated to 80°C at a rate of 35°C / min, kept at this temperature for 5 h, and cooled to 20°C in nitrogen at a rate of 40°C / min.

[0120] Example 10

[0121] This embodiment provides a method for preparing an aluminum oxide / a-IGZO thin film transistor, which includes the following steps:

[0122] (1) SiO2 / P + -Si substrate is fixed on the PLD sample holder, the target-substrate distance is controlled to 62mm, and the vacuum pump system is used to evacuate the cavity to a vacuum degree better than 5×10 -5 Pa, 3.6 Pa of 99.999% pure oxygen was filled into the cavity. A KrF excimer laser was used with a power of 10 J cm -2 With a laser energy per pulse, a repetition rate of 10 Hz, and a laser power of 200 mJ, a 35 nm thick a-IGZO film was deposited. The prepared a-IGZO film was patterned using photolithography, removing excess material while retaining photoresist at the electrode locations to determine the channel length and width.

[0123] (2) Patterned a-IGZO / SiO2 / P + -Si was placed in the PLD chamber again, and the sample was heated to 210°C at a rate of 35°C / min, kept at this temperature for 3 h, and cooled to 20°C with the furnace. During this period, the high vacuum in the PLD chamber was kept unchanged.

[0124] (3) Fix the alumina ceramic target on the PLD target holder, control the target-base distance to 62 mm, and use the vacuum pump system to evacuate the cavity to a vacuum degree better than 5×10 -5 Pa. A hollow metal tube with an inner diameter of 6 mm was used to fill the cavity with 5.0 Pa of 99.999% pure oxygen. The hollow metal tube was used as the cathode, the cavity was grounded, and a high-voltage DC power supply was used to apply an ionization voltage of 2.5 kV to the cathode to generate oxygen plasma in the cavity. A KrF laser was used at 10 J cm -2 With a laser energy of 100 mJ per pulse, a repetition rate of 10 Hz, and a laser power of 200 mJ, an 85 nm thick Al2O3 film was deposited. After deposition, the film was removed from the chamber.

[0125] (4) Remove the photoresist from the sample surface and use photolithography to define the source and drain locations of the transistor. Use radio frequency magnetron sputtering to deposit 100nm of Mo as the source and drain electrodes. After deposition, remove the photoresist from the sample surface to obtain a complete thin film transistor.

[0126] (5) The prepared thin film transistor was placed in a high vacuum PLD chamber again, and the sample was heated to 100°C at a rate of 35°C / min, kept at this temperature for 12 h, and cooled to 20°C in nitrogen at a rate of 20°C / min.

[0127] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing an aluminum oxide / a-IGZO thin film transistor, characterized in that: The following steps are involved: Step 1: Patterned a-IGZO / SiO2 / P + -Si is placed in a PLD chamber, heated to 100°C to 220°C under vacuum conditions, kept at this temperature for 3 to 12 hours for the first annealing, and then cooled to obtain a first process sample; Step 2: The first process sample is placed in a PLD chamber, using alumina ceramic as a target. Oxygen is introduced into the PLD chamber through a hollow metal tube. The PLD chamber is grounded, and the hollow metal tube serves as a cathode. A high-voltage DC power supply applies an ionization voltage to the cathode. The alumina ceramic target is sputtered by a KrF laser to deposit an Al2O3 thin film on the a-IGZO of the first process sample, thereby obtaining a second process sample. Step 3, removing the photoresist on the surface of the second process, preparing source and drain electrodes on the second process sample, and obtaining a third process sample; Step 4: anneal the sample from the third process for a second time at 80° C. to 140° C. under vacuum conditions for 3 to 12 hours, and obtain an aluminum oxide / a-IGZO thin film transistor after cooling.

2. The method for preparing an aluminum oxide / a-IGZO thin film transistor according to claim 1, wherein: In step 1, the vacuum pressure is ≤5×10 -5 Pa.

3. The method for preparing an aluminum oxide / a-IGZO thin film transistor according to claim 1, wherein: In step 2, before oxygen is filled, the PLD chamber is vacuumed to a vacuum degree of ≤5×10 -5 Pa.

4. The method for preparing an aluminum oxide / a-IGZO thin film transistor according to claim 1, wherein: In step 2, the oxygen partial pressure after filling is 4.5–6.0 Pa.

5. The method for preparing an aluminum oxide / a-IGZO thin film transistor according to claim 1, wherein: In step 2, the ionization voltage is 0.5–3.0 kV; the frequency of KrF laser sputtering is 1–10 Hz, and the laser power is 200–600 mJ.

6. The method for preparing an aluminum oxide / a-IGZO thin film transistor according to claim 1, wherein: In step 2, the thickness of the Al2O3 film is 60 to 100 nm.

7. The method for preparing an aluminum oxide / a-IGZO thin film transistor according to claim 1, characterized in that: In step 3, the source and drain electrodes are made of Mo, and the thickness of the source and drain electrodes is 100 nm.

8. The method for preparing an aluminum oxide / a-IGZO thin film transistor according to claim 1, wherein: In step 4, the vacuum condition of the third process sample is vacuum degree ≤ 5×10 -5 Pah.

9. The method for preparing an aluminum oxide / a-IGZO thin film transistor according to claim 1, wherein: In step 1, the patterned a-IGZO / SiO2 / P + -Si preparation process is: SiO2 / P + -Si substrate is fixed in the PLD chamber, and the vacuum degree of the PLD chamber is pumped to ≤5×10 -5 Pa, 3.2~3.7Pa of oxygen was filled into the PLD cavity; KrF laser was used at 10Jcm -2 Laser energy per pulse, repetition rate of 1-10Hz, laser power of 200-600mJ, in SiO2 / P + -Si substrate and deposited 20 to 40 nm thick a-IGZO thin film.

10. An aluminum oxide / a-IGZO thin film transistor prepared by the preparation method according to any one of claims 1 to 9, characterized in that: Aluminum oxide is deposited on the a-IGZO thin film in the thin film transistor as a passivation layer.

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