Metal oxide thin film transistor preparation method and metal oxide thin film transistor

Abstract

The invention belongs to the technical field of semiconductor devices, and relates to a preparation method of a metal oxide thin film transistor and the metal oxide thin film transistor. An insulating substrate is provided, and after a metal oxide semiconductor thin film is formed on the surface of the insulating substrate, annealing treatment is performed in a non-oxidizing atmosphere at the temperature higher than 350 DEG C; and then carrying out annealing treatment in an oxidizing atmosphere greater than or equal to 350 DEG C so as to prepare the metal oxide thin film transistor after annealing treatment. Balance between defect generation and passivation is achieved, effective defect regulation and control can be achieved, the stability of the metal oxide semiconductor thin film and the interface structure can be guaranteed, finally, the threshold voltage variation of the metal oxide thin film transistor before and after annealing is smaller than 0.5 V, the switching characteristic of a device is not affected, the sub-threshold swing is improved by at least 0.1 V / decade, and the performance of the device is improved. And the sub-threshold swing is improved while other performance parameters of the device are not influenced, so that the application requirement of high-gray-scale display is met.

Description

Technical Field

[0001] This invention relates to the field of semiconductor device technology, and in particular to a method for fabricating metal oxide thin-film transistors and the metal oxide thin-film transistor itself. Background Technology

[0002] Metal-oxide thin-film transistors (MO-TFTs) are key components in the flat panel display field, playing a central switching and driving role in active matrix driving technology. In liquid crystal displays (LCDs) and organic light-emitting diode displays (OLEDs), MO-TFTs constitute the driving circuit of the pixel array, controlling the charging and discharging process of pixel units or the on / off state of current paths through gate voltage.

[0003] Compared to traditional amorphous silicon TFTs, metal oxide TFTs have higher electron mobility (up to 100%). Metal oxide TFTs (MO-TFTs) facilitate higher pixel density and faster response times, thus meeting the demands of high-resolution displays. Furthermore, MO-TFTs exhibit excellent uniformity, low off-state current, and good stability, contributing to reduced power consumption and improved display contrast. In addition, metal oxide materials support low-temperature fabrication processes and are compatible with flexible substrates, laying the foundation for the development of flexible and transparent display technologies. Currently, metal oxide TFTs, represented by indium gallium zinc oxide (IGZO), are widely used in high-end smartphones, tablets, and laptops.

[0004] In the subthreshold region of a TFT, the drain current is exponentially related to the gate voltage. Therefore, a small change in the gate voltage can cause a significant change in the drain current. Based on this characteristic, the TFT can operate in the subthreshold region and achieve fine adjustment of the pixel charging current or OLED driving current by precisely controlling the gate voltage, thereby achieving more accurate grayscale control and supporting higher grayscale accuracy. This is especially suitable for high-resolution and high-contrast display applications. Subthreshold swing (SS) is an important parameter for evaluating the switching characteristics of a transistor. It is defined as the change in drain current caused by a change of one order of magnitude in the gate voltage. From the perspective of high grayscale display, the larger the subthreshold swing, the better. This is the opposite of the requirement in integrated circuits that the subthreshold swing of MOSFETs should be as small as possible in order to reduce power consumption. High grayscale display requires the driving device to output continuous and distinguishable multiple levels of current, that is, each level of current corresponds to a grayscale brightness. Small differences in current will be directly reflected in the subtle changes in screen brightness. When SS is large, the same gate voltage step value can drive a greater difference in drain current, and the current difference between adjacent grayscales is more obvious. The human eye can clearly distinguish different brightness levels and avoid grayscale adhesion. If SS is small, the current change is weak under the same gate voltage step, and the brightness difference between adjacent grayscales is difficult to distinguish, which will limit the number of grayscales displayed and make it impossible to achieve a delicate high grayscale display.

[0005] In summary, existing MO-TFT fabrication methods typically aim to reduce the subthreshold swing of the device, resulting in MO-TFTs with low subthreshold swing that cannot meet the application requirements of high grayscale displays. Summary of the Invention

[0006] Therefore, the technical problem to be solved by the present invention is to overcome the problem that the existing MO-TFT fabrication methods usually aim to reduce the subthreshold swing of the device, resulting in MO-TFTs with low subthreshold swing, which cannot meet the application requirements of high grayscale displays.

[0007] To solve the above-mentioned technical problems, the present invention provides a method for fabricating metal oxide thin-film transistors, characterized in that it includes: Provide an insulating substrate; After forming a metal oxide semiconductor thin film on the surface of an insulating substrate, the film is first annealed in a non-oxidizing atmosphere at a temperature greater than 350°C, and then annealed in an oxidizing atmosphere at a temperature greater than or equal to 350°C, thereby preparing an annealed metal oxide thin film transistor.

[0008] Preferably, the subthreshold swing of the annealed metal oxide thin film transistor is increased by 0.1V / decade to 0.75V / decade compared with that of the unannealed metal oxide thin film transistor.

[0009] Preferably, after forming a metal oxide semiconductor thin film on the surface of an insulating substrate, the film is first annealed in a non-oxidizing atmosphere at a temperature greater than 350°C, and then annealed in an oxidizing atmosphere at a temperature greater than or equal to 350°C to prepare an annealed metal oxide thin film transistor, comprising: A gate and a gate insulating layer are fabricated on the surface of an insulating substrate; A metal oxide semiconductor thin film is formed on the side of the gate insulating layer away from the gate, and the metal oxide semiconductor thin film is patterned to form a metal oxide semiconductor active island. Source and drain electrodes are formed to contact the active island of the metal oxide semiconductor, resulting in an unannealed metal oxide thin film transistor. The metal oxide thin film transistor is first annealed in a non-oxidizing atmosphere at a temperature greater than 350°C, and then annealed in an oxidizing atmosphere at a temperature greater than or equal to 350°C to obtain an annealed metal oxide thin film transistor.

[0010] Preferably, after forming a metal oxide semiconductor thin film on the surface of an insulating substrate, the film is first annealed in a non-oxidizing atmosphere at a temperature greater than 350°C, and then annealed in an oxidizing atmosphere at a temperature greater than or equal to 350°C to prepare an annealed metal oxide thin film transistor, comprising: A gate and a gate insulating layer are fabricated on the surface of an insulating substrate; A metal oxide semiconductor thin film is formed on the side of the gate insulating layer away from the gate, and the metal oxide semiconductor thin film is patterned to form a metal oxide semiconductor active island. The active island of the metal oxide semiconductor is first annealed in a non-oxidizing atmosphere at a temperature greater than 350°C, and then annealed in an oxidizing atmosphere at a temperature greater than or equal to 350°C. Source and drain electrodes are formed to contact the active island of the annealed metal oxide semiconductor, thereby obtaining the annealed metal oxide thin film transistor.

[0011] Preferably, after forming a metal oxide semiconductor thin film on the surface of an insulating substrate, the film is first annealed in a non-oxidizing atmosphere at a temperature greater than 350°C, and then annealed in an oxidizing atmosphere at a temperature greater than or equal to 350°C to prepare an annealed metal oxide thin film transistor, comprising: A gate and a gate insulating layer are fabricated on the surface of an insulating substrate; A metal oxide semiconductor thin film is formed on the side of the gate insulating layer away from the gate, and the metal oxide semiconductor thin film is patterned to form a metal oxide semiconductor active island. The active island of the metal oxide semiconductor is annealed in a non-oxidizing atmosphere at a temperature greater than 350°C. The source and drain electrodes are formed in contact with the active island of the metal oxide semiconductor after annealing in a non-oxidizing atmosphere; The active island of the metal oxide semiconductor is annealed in an oxidizing atmosphere at a temperature of 350°C or higher to obtain the annealed metal oxide thin film transistor.

[0012] Preferably, after forming a metal oxide semiconductor thin film on the surface of an insulating substrate, the film is first annealed in a non-oxidizing atmosphere at a temperature greater than 350°C, and then annealed in an oxidizing atmosphere at a temperature greater than or equal to 350°C to prepare an annealed metal oxide thin film transistor, comprising: A gate insulating layer is prepared on the surface of an insulating substrate; A metal oxide semiconductor thin film is formed on the side of the gate insulating layer away from the gate, and the metal oxide semiconductor thin film is patterned to form a metal oxide semiconductor active island. The active island of the metal oxide semiconductor is first annealed in a non-oxidizing atmosphere at a temperature greater than 350°C, and then annealed in an oxidizing atmosphere at a temperature greater than or equal to 350°C. Gate, source, and drain electrodes are formed on the active island of the annealed metal oxide semiconductor to obtain the annealed metal oxide thin film transistor.

[0013] Preferably, the annealing treatment is carried out at 400°C in a non-oxidizing atmosphere for at least 2 hours; Annealing is performed at 350°C in an oxidizing atmosphere for at least 2 hours.

[0014] Preferably, the non-oxidizing atmosphere is nitrogen, argon, or vacuum; The oxidizing atmosphere is oxygen, air, ozone, or a mixture of oxygen-containing gases.

[0015] Preferably, the annealing process is heated by resistance wire heating, halogen lamp irradiation heating, or laser irradiation heating.

[0016] The present invention also provides a metal oxide thin film transistor, which is prepared by the above-described method for preparing metal oxide thin film transistors.

[0017] The method for fabricating metal-oxide thin-film transistors provided in this application has the following advantages: After preparing the metal oxide semiconductor thin film, annealing is first performed in a non-oxidizing atmosphere. This process introduces defects such as oxygen vacancies into the film. Then, annealing is performed in an oxidizing atmosphere, which effectively passivates repairable defects in the film. Through two annealing processes, the subthreshold swing of the device can be controlled. Based on this, this application discovers that high-temperature (above 350°C) non-oxygen annealing in an oxygen-deficient environment can controllably generate defects such as oxygen vacancies within the metal oxide semiconductor thin film, effectively controlling the carrier concentration and defect state distribution within the film. Subsequent annealing in an oxidizing atmosphere at 350°C or higher can further control repairable deep-level defects and boundary defects in the metal oxide semiconductor thin film without compromising the previous control effects. Selective passivation of surface defects is achieved by combining annealing in a non-oxidizing atmosphere above 350°C with annealing in an oxidizing atmosphere above or equal to 350°C. This balances defect generation and passivation, enabling effective defect control while ensuring the stability of the metal oxide semiconductor thin film and interface structure. This effectively improves the subthreshold swing of the device, ultimately resulting in a turn-on voltage change of less than 0.5V before and after annealing, without affecting the switching characteristics of the device. Furthermore, the subthreshold swing of the device after two annealing cycles is increased by 0.1V / decade to 0.75V / decade compared to before the two annealing cycles. This improvement in the subthreshold swing without affecting other performance parameters of the device allows it to meet the application requirements of high grayscale displays. Attached Figure Description

[0018] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein: Figure 1 This is a flowchart of the metal oxide thin-film transistor fabrication method provided in this application; Figure 2 The transfer curves of metal oxide thin-film transistors before and after nitrogen annealing at different temperatures are provided in this application; wherein, Figure 2 (a) shows the transfer curves of the metal oxide thin-film transistor before and after nitrogen annealing at 350℃. Figure 2 (b) shows the transfer curves of the metal oxide thin film transistor before and after nitrogen annealing at 400℃; Figure 3 The transfer curves of the metal oxide thin film transistor before and after oxygen annealing at 350°C provided in this application; Figure 4 The transfer curves of metal oxide thin-film transistors before and after nitrogen annealing and oxygen annealing at different temperatures provided in this application; wherein, Figure 4 (a) shows the transfer curves of the metal oxide thin-film transistor before and after nitrogen annealing at 350℃ and oxygen annealing at 350℃. Figure 4(b) shows the transfer curves of the metal oxide thin film transistor before and after nitrogen annealing at 400℃ and oxygen annealing at 350℃. Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0020] In existing integrated circuit applications, methods to reduce power consumption and lower the subthreshold swing of metal oxide thin-film transistors (TFTs) have been proposed. One approach is to change the gate insulating layer material. In mature TFT processes, a commonly used gate dielectric is a stack of silicon dioxide and silicon nitride. Some studies have employed high-k dielectrics (e.g., , One approach is to replace traditional silicon dioxide to enhance the gate's control over the channel and reduce the device's subthreshold swing. From this perspective, using an insulator with a lower dielectric constant can help increase the device's subthreshold swing. However, there is no relevant research in the current technology, and insulators with lower dielectric constants cannot simultaneously guarantee the transistor's normal switching characteristics and a high subthreshold swing. Another approach is to change the device structure, using dual-gate, triple-gate, or gate-all-around structures, and thinning the channel layer to enhance the gate's control over the channel, thereby reducing the device's subthreshold swing. From this perspective, increasing the thickness of the semiconductor active layer in the device is also a way to increase the device's subthreshold swing. However, increasing the active layer thickness will also increase the device's off-state current and off-state leakage current, thus increasing the device's power consumption.

[0021] To improve the subthreshold swing of metal-oxide-slim transistors (MOSFETs) for better application in high grayscale displays, while ensuring normal switching characteristics, low leakage current, and low power consumption, this application proposes a method for fabricating MOSFETs, such as... Figure 1 As shown, the method specifically includes: S10: Provide an insulating substrate.

[0022] S20: After forming a metal oxide semiconductor thin film on the surface of an insulating substrate, the film is first annealed in a non-oxidizing atmosphere at a temperature greater than 350°C, and then annealed in an oxidizing atmosphere at a temperature greater than or equal to 350°C, thereby obtaining an annealed metal oxide thin film transistor.

[0023] Furthermore, the non-oxidizing atmosphere is nitrogen, argon, or vacuum; the oxidizing atmosphere is oxygen, air, ozone, or an oxygen-containing mixture.

[0024] Furthermore, the annealing process is heated by resistance wire heating, halogen lamp irradiation heating, or laser irradiation heating.

[0025] This application, through experimental research, discovers that a two-step annealing process after the formation of a metal oxide thin film significantly improves defect control and device electrical performance. Specifically, annealing is first performed in a non-oxidizing atmosphere, which introduces defects such as oxygen vacancies into the film. Then, annealing is performed in an oxidizing atmosphere, which effectively passivates repairable defects in the film. This two-step annealing process allows for precise control of the device's subthreshold swing. Another technical challenge this application addresses is determining and obtaining the temperature range within which the two annealing processes synergistically enhance the device's subthreshold swing. Specifically, high-temperature annealing above 350°C in an oxygen-deficient environment allows for the controllable generation of defects such as oxygen vacancies within the metal oxide semiconductor thin film, effectively controlling the carrier concentration and defect state distribution within the film. Based on this, a further step is taken... Secondary annealing in an oxidizing atmosphere at or above 350°C can selectively passivate repairable deep-level and interface defects in metal-oxide-semiconductor thin films without compromising the effects of the preceding control. However, if the first annealing temperature is below or above 350°C, insufficient defect generation will result, and if the second annealing temperature is below 350°C, inadequate defect passivation will also occur. Therefore, combining annealing in a non-oxidizing atmosphere above 350°C with annealing in an oxidizing atmosphere above or above 350°C can achieve a balance between defect generation and passivation, enabling effective defect control while ensuring the stability of the metal-oxide-semiconductor thin film and interface structure, and effectively improving the subthreshold swing of the device.

[0026] Specifically, this application provides the effects of annealing in non-oxidizing and oxidizing atmospheres at different temperatures on the characteristics of metal oxide thin-film transistors: like Figure 2 The figure shows the transfer curves of the metal oxide thin-film transistor before and after nitrogen annealing at different temperatures provided in this application; wherein, Figure 2 (a) shows the transfer curves of the metal oxide thin-film transistor before and after nitrogen annealing at 350℃. Figure 2 (b) shows the transfer curves of the metal oxide thin film transistor before and after nitrogen annealing at 400℃.

[0027] from Figure 2 As can be seen, the transition curve of the device will exhibit significant drift only when nitrogen annealed at 350℃ for 2 hours. The turn-on voltage corresponding to the device transitioning from the off state to the subthreshold region will decrease significantly, from 1V to -7.2V, and the subthreshold swing will increase from 1.25V / dec to 1.73V / dec. The device will short-circuit and cannot be turned off only when nitrogen annealed at 400℃ for 2 hours.

[0028] like Figure 3 The transfer curves of the metal oxide thin-film transistor before and after oxygen annealing at 350°C provided in this application are from...Figure 3 As can be seen, the transfer curve of the device only showed a slight positive drift after 2 hours of oxygen annealing at 350℃. The turn-on voltage increased from 0.45V to 0.91V, while the subthreshold swing remained almost unchanged at 1.3V / dec.

[0029] Figure 4 The transfer curves of metal oxide thin-film transistors before and after nitrogen annealing and oxygen annealing at different temperatures provided in this application; wherein, Figure 4 (a) shows the transfer curves of the metal oxide thin-film transistor before and after nitrogen annealing at 350℃ and oxygen annealing at 350℃. Figure 4 (b) shows the transfer curves of the metal oxide thin film transistor before and after nitrogen annealing at 400℃ and oxygen annealing at 350℃.

[0030] from Figure 4 As can be seen, after annealing in nitrogen at 350℃ for 2 hours, followed by annealing in oxygen at 350℃ for 2 hours, the negative drift of the device's transfer curve recovers, and the turn-on voltage and subthreshold swing return to their initial values. Figure 2 The data shows that if the device is annealed in nitrogen at 400℃ for 2 hours, it will short-circuit and cannot be turned off. However, after annealing in nitrogen at 400℃ for 2 hours and then in oxygen at 350℃ for 2 hours, the device's turn-on voltage returns to its initial value, and the off-state leakage current is also consistent with the initial value. The device's subthreshold swing increases from 1.22V / dec to 1.97V / dec. The subthreshold swing of the device after annealing is 0.75V / dec higher than before annealing. This shows that simply annealing in nitrogen or oxygen can increase the device's subthreshold swing. Controlling the temperature of annealing in a non-oxidizing atmosphere or an oxidizing atmosphere alone cannot achieve the effect of improving the device's subthreshold swing without affecting the device's switching characteristics.

[0031] Specifically, this application, combined with TCAD software simulation analysis, found that the defects added in the channel of the device after nitrogen annealing at 350℃ are mainly donor defects, primarily oxygen vacancy defects. Oxygen vacancy defects can be filled by oxygen diffused from the atmosphere into the metal oxide semiconductor film during annealing in an oxygen-containing atmosphere, so the transferred defects can be restored to their initial values ​​after oxygen annealing. In addition to donor defects, the defects added in the channel of the device after nitrogen annealing at 400℃ also include acceptor defects. In the metal oxide semiconductor film, these are mainly oxygen atoms at interstitial positions. During the 350℃ oxygen atmosphere annealing process, donor defects are filled by oxygen diffused from the atmosphere into the metal oxide semiconductor film, while interstitial oxygen atom defects cannot be eliminated. Therefore, the interstitial oxygen atom defects remaining in the metal oxide semiconductor film increase the subthreshold swing of the device.

[0032] Preferably, the annealing treatment is performed at 400°C in a non-oxidizing atmosphere for at least 2 hours; or at 350°C in an oxidizing atmosphere for at least 2 hours.

[0033] Furthermore, the subthreshold swing of the annealed metal oxide thin film transistor is increased by 0.1V / decade to 0.75V / decade compared to the unannealed metal oxide thin film transistor.

[0034] Table 1 shows the changes in turn-on voltage and subthreshold swing of metal oxide thin-film transistors after nitrogen annealing and oxygen annealing in several comparative examples and embodiments provided in this application, compared to the turn-on voltage and subthreshold swing of metal oxide thin-film transistors without annealing: Table 1

[0035] As shown in Table 1, in Comparative Example 1, when the nitrogen annealing temperature is less than or equal to 350℃ and the oxygen annealing temperature is less than 300℃, although the subthreshold swing of the device increases, the turn-on voltage of the device changes significantly, indicating that the two annealing processes affect the switching characteristics of the device. In Comparative Example 2, when both the nitrogen and oxygen annealing temperatures are equal to 350℃, the switching characteristics and subthreshold swing of the device do not change. In Comparative Example 3, when the nitrogen annealing temperature reaches 400℃ and the oxygen annealing temperature is less than 350℃, although the subthreshold swing of the device increases, the large number of defects generated by nitrogen annealing and the insufficient passivation of defects by oxygen annealing, as well as the insufficient interface state repair, lead to a 10V reduction in the turn-on voltage of the device, thus severely affecting the switching characteristics of the device. Examples In Example 1, when the nitrogen annealing temperature is 400℃ and the oxygen annealing temperature is 350℃, the device's turn-on voltage remains unchanged, while the subthreshold swing increases by 0.75V / decade. The device improves the subthreshold swing without affecting its switching characteristics, indicating that the synergistic effect of nitrogen and oxygen annealing achieves better controllability of the subthreshold swing. This can expand the device's applicability in different driving scenarios and power consumption requirements, especially in the field of high grayscale displays. In Example 2, when the nitrogen annealing temperature is maintained at 400℃ and the oxygen annealing temperature is increased to 400℃, the device's subthreshold swing increases by 0.65V / decade compared to before annealing. Although the turn-on voltage also increases slightly, it still does not affect the device's switching characteristics.

[0036] Furthermore, in some embodiments, step S20 includes S200~S203: S200: The gate and gate insulating layer are prepared on the surface of the insulating substrate.

[0037] S201: A metal oxide semiconductor thin film is formed on the side of the gate insulating layer away from the gate, and the metal oxide semiconductor thin film is patterned to form a metal oxide semiconductor active island.

[0038] S202: Form source and drain electrodes that are in contact with the active island of the metal oxide semiconductor to obtain an unannealed metal oxide thin film transistor.

[0039] S203: First, the metal oxide thin film transistor is annealed in a non-oxidizing atmosphere at a temperature greater than 350°C, and then the metal oxide thin film transistor is annealed in an oxidizing atmosphere at a temperature greater than or equal to 350°C, thereby obtaining the annealed metal oxide thin film transistor.

[0040] In some other embodiments, step S20 includes S210 to S213: S210: Prepare the gate and gate insulating layer on the surface of the insulating substrate.

[0041] S211: A metal oxide semiconductor thin film is formed on the side of the gate insulating layer away from the gate, and the metal oxide semiconductor thin film is patterned to form a metal oxide semiconductor active island.

[0042] S212: First, the active island of the metal oxide semiconductor is annealed in a non-oxidizing atmosphere at a temperature greater than 350°C, and then the active island of the metal oxide semiconductor is annealed in an oxidizing atmosphere at a temperature greater than or equal to 350°C.

[0043] S213: Form source and drain electrodes that are in contact with the active island of the annealed metal oxide semiconductor to obtain the annealed metal oxide thin film transistor.

[0044] In some other embodiments, step S20 includes S220~S224: S220: A gate and gate insulating layer are prepared on the surface of an insulating substrate.

[0045] S221: A metal oxide semiconductor thin film is formed on the side of the gate insulating layer away from the gate, and the metal oxide semiconductor thin film is patterned to form a metal oxide semiconductor active island.

[0046] S222: Annealing of active islands of metal oxide semiconductors in a non-oxidizing atmosphere at a temperature greater than 350°C.

[0047] S223: Forms the source and drain electrodes that are in contact with the active island of the metal oxide semiconductor after annealing in a non-oxidizing atmosphere.

[0048] S224: Annealing the active island of a metal oxide semiconductor at an oxidizing atmosphere of 350°C or higher yields an annealed metal oxide thin film transistor.

[0049] In some other embodiments, step S20 includes S230~S233: S230: Prepare a gate insulating layer on the surface of an insulating substrate.

[0050] S231: A metal oxide semiconductor thin film is formed on the side of the gate insulating layer away from the gate, and the metal oxide semiconductor thin film is patterned to form a metal oxide semiconductor active island.

[0051] S232: First, the active island of the metal oxide semiconductor is annealed in a non-oxidizing atmosphere at a temperature greater than 350°C, and then the active island of the metal oxide semiconductor is annealed in an oxidizing atmosphere at a temperature greater than or equal to 350°C.

[0052] S233: A gate, source, and drain electrode are formed on the annealed metal oxide semiconductor active island to obtain an annealed metal oxide thin film transistor.

[0053] This application, through extensive experimental and mechanistic studies, has discovered that, in addition to performing non-oxidizing atmosphere annealing followed by oxidizing atmosphere annealing after fabrication of metal oxide thin-film transistors (MOSTs), the combination of non-oxidizing atmosphere annealing and oxidizing atmosphere annealing at different process nodes after MOST thin film fabrication can also achieve the same effect of improving the device's subthreshold swing. This indicates that the two-step annealing process combining non-oxidizing atmosphere annealing and oxidizing atmosphere annealing within a specific temperature range proposed in this application is not limited to a specific process sequence or a single processing node, but possesses broad process compatibility and universality. Whether after MOST thin film deposition, before or after gate structure fabrication, before or after source / drain electrode fabrication, or in the post-processing stage of overall device formation, as long as the processing is combined in the order of first annealing at a temperature greater than 350°C and then annealing at a temperature greater than or equal to 350°C, the film quality, interface state density, and defect distribution of the MOST can be effectively controlled. This allows for a stable and reliable improvement in the device's subthreshold swing and subthreshold transport characteristics without affecting the device's switching characteristics.

[0054] Based on the metal oxide thin film transistor fabrication method provided in the above embodiments, this application also provides a metal oxide thin film transistor fabricated using the same method.

[0055] In summary, the metal oxide thin-film transistor fabrication method provided in this application, without altering the device structure and materials, achieves a device turn-on voltage change of less than 0.5V compared to before annealing by introducing a two-step annealing process with both a non-oxidizing atmosphere and an oxidizing atmosphere in the fabrication process. This requires only controlling the temperature of the two annealing steps. Simultaneously, the subthreshold swing is increased by 0.1V / decade to 0.75V / decade compared to before annealing. Since the device structure and materials are not altered, the problems of material changes affecting the device's switching characteristics and structural changes increasing power consumption are avoided. Ultimately, the subthreshold swing is improved while maintaining the normal switching characteristics of the transistor and without increasing power consumption. This provides a stable, reliable, and process-compatible control method for high grayscale display applications, effectively improving the grayscale control accuracy, image layering, and image detail of the display panel, meeting the practical application requirements of high-end display panels for low power consumption, high uniformity, and high image quality.

[0056] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for fabricating a metal oxide thin-film transistor, characterized in that, include: Provide an insulating substrate; After forming a metal oxide semiconductor thin film on the surface of an insulating substrate, the film is first annealed in a non-oxidizing atmosphere at a temperature greater than 350°C, and then annealed in an oxidizing atmosphere at a temperature greater than or equal to 350°C, thereby preparing an annealed metal oxide thin film transistor.

2. The method for fabricating a metal oxide thin-film transistor according to claim 1, characterized in that, The subthreshold swing of the annealed metal oxide thin film transistor is increased by 0.1V / decade to 0.75V / decade compared with that of the unannealed metal oxide thin film transistor.

3. The method for fabricating a metal oxide thin-film transistor according to claim 1, characterized in that, After forming a metal oxide semiconductor thin film on the surface of an insulating substrate, the film is first annealed in a non-oxidizing atmosphere at a temperature greater than 350°C, and then annealed in an oxidizing atmosphere at a temperature greater than or equal to 350°C to prepare an annealed metal oxide thin film transistor, comprising: A gate and a gate insulating layer are fabricated on the surface of an insulating substrate; A metal oxide semiconductor thin film is formed on the side of the gate insulating layer away from the gate, and the metal oxide semiconductor thin film is patterned to form a metal oxide semiconductor active island. Source and drain electrodes are formed to contact the active island of the metal oxide semiconductor, resulting in an unannealed metal oxide thin film transistor. The metal oxide thin film transistor is first annealed in a non-oxidizing atmosphere at a temperature greater than 350°C, and then annealed in an oxidizing atmosphere at a temperature greater than or equal to 350°C to obtain an annealed metal oxide thin film transistor.

4. The method for fabricating a metal oxide thin-film transistor according to claim 1, characterized in that, After forming a metal oxide semiconductor thin film on the surface of an insulating substrate, the film is first annealed in a non-oxidizing atmosphere at a temperature greater than 350°C, and then annealed in an oxidizing atmosphere at a temperature greater than or equal to 350°C to prepare an annealed metal oxide thin film transistor, comprising: A gate and a gate insulating layer are fabricated on the surface of an insulating substrate; A metal oxide semiconductor thin film is formed on the side of the gate insulating layer away from the gate, and the metal oxide semiconductor thin film is patterned to form a metal oxide semiconductor active island. The active island of the metal oxide semiconductor is first annealed in a non-oxidizing atmosphere at a temperature greater than 350°C, and then annealed in an oxidizing atmosphere at a temperature greater than or equal to 350°C. Source and drain electrodes are formed to contact the active island of the annealed metal oxide semiconductor, thereby obtaining the annealed metal oxide thin film transistor.

5. The method for fabricating a metal oxide thin-film transistor according to claim 1, characterized in that, After forming a metal oxide semiconductor thin film on the surface of an insulating substrate, the film is first annealed in a non-oxidizing atmosphere at a temperature greater than 350°C, and then annealed in an oxidizing atmosphere at a temperature greater than or equal to 350°C to prepare an annealed metal oxide thin film transistor, comprising: A gate and a gate insulating layer are fabricated on the surface of an insulating substrate; A metal oxide semiconductor thin film is formed on the side of the gate insulating layer away from the gate, and the metal oxide semiconductor thin film is patterned to form a metal oxide semiconductor active island. The active island of the metal oxide semiconductor is annealed in a non-oxidizing atmosphere at a temperature greater than 350°C. The source and drain electrodes are formed in contact with the active island of the metal oxide semiconductor after annealing in a non-oxidizing atmosphere; The active island of the metal oxide semiconductor is annealed in an oxidizing atmosphere at a temperature of 350°C or higher to obtain the annealed metal oxide thin film transistor.

6. The method for fabricating a metal oxide thin-film transistor according to claim 1, characterized in that, After forming a metal oxide semiconductor thin film on the surface of an insulating substrate, the film is first annealed in a non-oxidizing atmosphere at a temperature greater than 350°C, and then annealed in an oxidizing atmosphere at a temperature greater than or equal to 350°C to prepare an annealed metal oxide thin film transistor, comprising: A gate insulating layer is prepared on the surface of an insulating substrate; A metal oxide semiconductor thin film is formed on the side of the gate insulating layer away from the gate, and the metal oxide semiconductor thin film is patterned to form a metal oxide semiconductor active island. The active island of the metal oxide semiconductor is first annealed in a non-oxidizing atmosphere at a temperature greater than 350°C, and then annealed in an oxidizing atmosphere at a temperature greater than or equal to 350°C. Gate, source, and drain electrodes are formed on the active island of the annealed metal oxide semiconductor to obtain the annealed metal oxide thin film transistor.

7. The method for fabricating a metal oxide thin-film transistor according to claim 1, characterized in that, Annealing at 400°C in a non-oxidizing atmosphere for at least 2 hours; Annealing is performed at 350°C in an oxidizing atmosphere for at least 2 hours.

8. The method for fabricating a metal oxide thin-film transistor according to claim 1, characterized in that, The non-oxidizing atmosphere is nitrogen, argon, or vacuum; The oxidizing atmosphere is oxygen, air, ozone, or a mixture of oxygen-containing gases.

9. The method for fabricating a metal oxide thin-film transistor according to claim 1, characterized in that, The annealing process is heated by resistance wire heating, halogen lamp irradiation heating, or laser irradiation heating.

10. A metal oxide thin-film transistor, characterized in that, The metal oxide thin film transistor is prepared by the metal oxide thin film transistor preparation method according to any one of claims 1 to 9.

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