CN113661574B - Display substrate, preparation method thereof and display panel - Google Patents

Abstract

A display substrate, a preparation method thereof and a display panel aim at improving the structure of the display substrate, improving the characteristics of a thin film transistor and improving the yield of display products. Wherein, the display substrate includes: a substrate base (1); a thin film transistor (2) located on the substrate base plate (1); a first passivation layer (3) located on a side of the thin film transistor (2) facing away from the substrate base plate (1); the oxygen supplementing layer (4) is positioned on one side, deviating from the substrate base plate (1), of the first passivation layer (3) and at least covers the channel region (20) of the thin film transistor (2), the oxygen content in the oxygen supplementing layer (4) is larger than that in the first passivation layer (3), and the contents of hydrogen, nitrogen and water molecules in the oxygen supplementing layer (4) are respectively smaller than those in the first passivation layer (3).

Description

Display substrate and preparation method thereof, and display panel

Technical Field

The present application relates to the field of display technology, and in particular to a display substrate and a preparation method thereof, and a display panel.

Background technique

Metal oxide thin film transistors (Oxide TFTs) have the advantages of high mobility, uniform device performance, suitability for large-area production, low preparation temperature, suitability for flexible display, wide bandgap, transparency under visible light, and suitability for transparent display. They are considered to be the most promising material to replace silicon-based materials and become the channel material of thin film transistors.

In oxide semiconductor thin film transistors (Oxide TFTs), oxygen vacancies (Vo) are very likely to appear in the channel region, which leads to deterioration of TFT stability, such as poor stability of the negative bias test (NBTIS) of TFTs under temperature and light. Therefore, reducing the Vo defect content in the channel and improving the stability of TFT performance are one of the important research directions of oxide TFTs.

Summary of the invention

The present application discloses a display substrate and a preparation method thereof, and a display panel, the purpose of which is to improve the structure of the display substrate, improve the characteristics of thin film transistors, and improve the yield of display products.

A display substrate, comprising:

substrate substrate;

A thin film transistor is located on the substrate;

A first passivation layer is located on a side of the thin film transistor away from the substrate;

The oxygen supplement layer is located on the side of the first passivation layer away from the substrate, and at least covers the channel region of the thin film transistor. The oxygen content in the oxygen supplement layer is greater than the oxygen content in the first passivation layer, and the contents of hydrogen, nitrogen and water molecules in the oxygen supplement layer are respectively less than the contents of hydrogen, nitrogen and water molecules in the first passivation layer.

Optionally, an orthographic projection pattern of the oxygen supplementing layer on the base substrate is the same as or substantially the same as an orthographic projection pattern of the first passivation layer on the base substrate.

Optionally, the material of the oxygen supplementing layer includes aluminum oxide.

Optionally, the material of the oxygen supplement layer includes silicon oxide.

Optionally, the material of the first passivation layer includes silicon oxide, and the refractive index of the first passivation layer is greater than the refractive index of the oxygen supplementation layer.

Optionally, the display substrate further includes a second passivation layer, which is located on the side of the oxygen supplement layer away from the base substrate; the oxygen content in the oxygen supplement layer is greater than the oxygen content in the second passivation layer, and the contents of hydrogen, nitrogen and water molecules in the oxygen supplement layer are respectively less than the contents of hydrogen, nitrogen and water molecules in the second passivation layer.

Optionally, the material of the oxygen supplement layer includes silicon oxide; the material of the second passivation layer includes silicon oxide, and the refractive index of the second passivation layer is greater than the refractive index of the oxygen supplement layer.

Optionally, the oxygen diffusion performance of the first passivation layer is better than that of the second passivation layer.

Optionally, the ratio of the thickness of the first passivation layer to the thickness of the oxygen supplement layer is 10-40; and the ratio of the thickness of the second passivation layer to the thickness of the oxygen supplement layer is 20-40.

A display panel comprises any one of the display substrates described above.

A method for preparing a display substrate comprises the following steps:

preparing a thin film transistor on a substrate;

preparing a first passivation layer on the thin film transistor;

An oxygen supplement layer is prepared on the first passivation layer, the oxygen supplement layer at least covers the channel region of the thin film transistor, the oxygen content in the oxygen supplement layer is greater than the oxygen content in the first passivation layer, and the contents of hydrogen, nitrogen and water molecules in the oxygen supplement layer are respectively less than the contents of hydrogen, nitrogen and water molecules in the first passivation layer.

Optionally, preparing a first passivation layer on the thin film transistor specifically includes:

The silicon oxide or silicon nitride film layer is deposited using the PECVD process, and the PECVD power density is less than 0.25W/cm2;

High temperature annealing is performed at a temperature above 300°C.

Optionally, preparing an oxygen supplementing layer on the first passivation layer specifically includes:

Using semiconductors, metals, semiconductor oxides or metal oxides as target materials, introducing a gas with an oxygen content greater than 50%, controlling the temperature of the film-forming substrate at greater than 100°C, and preparing an oxide film layer by magnetron sputtering.

Optionally, the target material includes Si, Al, SiOx, or AlOx.

Optionally, after preparing the oxygen supplement layer on the first passivation layer, the method further includes:

A silicon oxide or silicon nitride film layer is deposited by a PECVD process to prepare a second passivation layer, wherein the film forming temperature of the silicon oxide or silicon nitride film layer is greater than 300°C.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of a partial cross-sectional structure of a display substrate provided by an embodiment of the present application;

FIG2 is a flow chart of a method for preparing a display substrate provided in one embodiment of the present application;

3 is a schematic diagram of a partial cross-sectional structure of a display substrate when a first passivation layer is prepared according to an embodiment of the present application;

FIG4 is a schematic diagram of a partial cross-sectional structure of a display substrate when an oxygen supplementing layer is prepared according to an embodiment of the present application;

FIG. 5 is a schematic diagram of a partial cross-sectional structure of a display substrate when preparing a second passivation layer according to an embodiment of the present application.

Detailed ways

In oxide semiconductor thin film transistors (such as IGZO TFT), the introduction of H, N, _H2O and oxygen vacancies (Vo) can easily lead to deterioration of TFT stability. At present, the preparation route of conventional oxide TFT is generally to form a _SiOx passivation layer on the TFT through plasma chemical vapor deposition (PECVD) to supplement oxygen to the TFT channel and reduce Vo. However, the by-products of _SiOx thin films prepared by PECVD are relatively high, and H, N, _H2O , etc. are easily introduced during the film formation process. Therefore, it will still lead to deterioration of TFT stability and cannot effectively improve TFT stability.

In view of the above problems, the embodiments of the present application disclose a display substrate and a preparation method thereof, a display panel, and a display device, the purpose of which is to reduce oxygen vacancy (Vo) defects in the TFT channel region by improving the structure of the display substrate, and reduce TFT defects caused by the introduction of H, N and _H2O , thereby improving the characteristics of thin film transistors and improving the yield of display products.

The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

As shown in FIG1 , an embodiment of the present application provides a display substrate, including:

Base substrate 1;

A thin film transistor 2 is located on the substrate 1;

A first passivation layer 3 is located on a side of the thin film transistor 2 facing away from the substrate 1;

The add oxygen layer 4 (AOL) is located on the side of the first passivation layer 3 away from the substrate 1, and at least covers the channel region 20 of the thin film transistor 2. The oxygen content in the add oxygen layer 4 is greater than the oxygen content in the first passivation layer 3, and the contents of hydrogen (H), nitrogen (N) and water molecules ( _H2O ) in the add oxygen layer 4 are respectively less than the contents of hydrogen, nitrogen and water molecules in the first passivation layer 3.

In the display substrate provided in the embodiment of the present application, a first passivation layer 3 and an oxygen supplement layer 4 are sequentially provided above the thin film transistor 2 (TFT 2); the first passivation layer 3 can protect the thin film transistor (TFT) 2, the oxygen supplement layer 4 at least covers the channel region 20 of the thin film transistor 2, and the oxygen content in the oxygen supplement layer 4 is greater than the oxygen content in the first passivation layer 3, and the contents of H, N and H ₂ O are respectively less than the contents of H, N and H ₂ O in the first passivation layer 3, so that the oxygen supplement layer 4 can, on the one hand, provide sufficient oxygen elements to the channel region 20 of the TFT 2 to reduce the amount of oxygen vacancy (Vo) defects, and on the other hand, can also greatly reduce the introduction of H, N and H ₂ O to avoid the influence of H, N and H ₂ O on the stability of the TFT 2.

In summary, the above-mentioned display substrate can supplement oxygen elements for the TFT2 channel region 20 by adding an oxygen supplement layer 4 above the thin film transistor (TFT) 2, effectively reduce the oxygen vacancy (Vo) defects in the TFT 2 channel region 20, and reduce the TFT 2 defects caused by the introduction of H, N and _H2O , which can effectively improve the characteristics and stability of TFT 2 and improve the yield of display products.

As shown in FIG1 , in some embodiments, the thin film transistor 2 is a bottom gate structure, including a gate electrode 21, an active layer 22, a source electrode 24, and a drain electrode 23 arranged in sequence. The first passivation layer 3 is located above the TFT 2, directly covering the channel region 20 of the TFT 2, and the oxygen supplement layer 4 is located on the first passivation layer 3. The oxygen element of the oxygen supplement layer 4 can directly reach the channel region 20 of the TFT 2 through the first passivation layer 3, so as to reduce the oxygen vacancies (Vo) in the channel region 20 of the TFT 2.

Of course, the thin film transistor 2 in the embodiment of the present application may also be a top-gate structure, which is not limited here.

As shown in Fig. 1, in some embodiments, the orthographic projection pattern of the oxygen supplementing layer 4 on the base substrate 1 is the same or substantially the same as the orthographic projection pattern of the first passivation layer 3 on the base substrate 1. 'Substantially the same' means that the shapes of the two patterns are the same or similar, and the pattern sizes are the same or similar.

Exemplarily, the oxygen replenishing layer 4 and the first passivation layer 3 may be the entire film layer covering the thin film transistor 2, and via holes penetrating the oxygen replenishing layer 4 and the first passivation layer 3 may be provided at locations where electrical connection between layers is required.

For example, as shown in FIG1 , the display substrate of the embodiment of the present application further includes structures such as a pixel electrode 7, a common electrode 8, and a common electrode connecting lead 9. The pixel electrode 7 and the common electrode connecting lead 9 are located above the oxygen supplement layer 4 and the first passivation layer 3; the common electrode 8 is arranged between the base substrate 1 and the gate insulating layer 6, and may include an electrode portion 81 and a lap portion 82, and the lap portion 82 may be prepared in the same layer as the gate 21 of the TFT 2 and lapped on the electrode portion 81. Specifically, the display substrate is provided with two vias penetrating the oxygen supplement layer 4 and the first passivation layer 3, such as a first via 101 and a second via 102, the pixel electrode 7 is electrically connected to the drain 23 of the TFT 2 through the first via 101, and the connecting lead 9 of the common electrode 8 is electrically connected to the lap portion 82 of the common electrode 8 through the second via 102.

In some embodiments, the material of the oxygen supplementing layer 4 includes aluminum oxide.

For example, the oxygen supplement layer may be an aluminum oxide film layer, which generally contains a large amount of excess oxygen (exO, i.e., weakly bonded oxygen that is easily released), and very little content of elements such as N, H, and H ₂ O. During the process of preparing the aluminum oxide film layer, it is easy for some oxygen elements to enter the channel region of the TFT, thereby performing oxygen compensation in the channel region of the TFT, reducing oxygen vacancies, and not introducing N, H, and H ₂ O.

In some embodiments, the material of the oxygen supplementing layer 4 includes silicon oxide.

Exemplarily, the oxygen supplement layer may be a silicon oxide film layer, which may contain a large amount of excess oxygen (exO), and in the process of preparing the silicon oxide film layer, it is easy for some oxygen elements to enter the channel region of the TFT, thereby performing oxygen compensation in the channel region of the TFT and reducing oxygen vacancies. In addition, by selecting the preparation process, it is possible to prevent N, H, H ₂ O, etc. from being introduced during the preparation of the silicon oxide film layer, and the content of N, H, and H ₂ O in the finally formed silicon oxide film layer can be very small.

In a specific embodiment, the material of the oxygen supplementing layer 4 includes silicon oxide, and the material of the first passivation layer 3 includes silicon oxide.

For example, the oxygen supplement layer 4 is a silicon oxide film layer, and the first passivation layer 3 is a silicon oxide film layer. Although both are silicon oxide films, the film properties of the oxygen supplement layer 4 and the first passivation layer 3 are different, such as the film refractive index, the purity of the silicon oxide material in the film, and the content of excess oxygen (exO) and N, H, _H2O , etc. in the film. For example:

Specifically, the refractive index of the first passivation layer 3 is greater than the refractive index of the oxygen supplementation layer 4. Exemplarily, the refractive index of the oxygen supplementation layer 4 is less than 1.45, and the refractive index of the first passivation layer 3 is greater than 1.45.

Specifically, compared with the first passivation layer 3 , the Si—O—Si stretching vibration peak in the oxygen supplementing layer 4 material moves toward a high wave number direction, has a narrower half-width, and has a higher purity of the silicon oxide material.

Specifically, the content of excess oxygen (exO) in the oxygen supplementing layer 4 is higher than that in the first passivation layer 3 , while the content of H, N, H ₂ O, etc. is much lower than that in the first passivation layer 3 .

As shown in Figure 1, in some embodiments, the display substrate of the embodiment of the present application may also include a second passivation layer 5, which is located on the side of the oxygen supplement layer 4 away from the base substrate 1; the oxygen content in the oxygen supplement layer 4 is greater than the oxygen content in the second passivation layer 5, and the contents of hydrogen, nitrogen and water molecules in the oxygen supplement layer 4 are respectively less than the contents of hydrogen, nitrogen and water molecules in the second passivation layer 5.

Specifically, the process of preparing the second passivation layer 5 can promote the excess oxygen in the oxygen supplement layer 4 to further diffuse into the channel region 20 of the TFT 2, thereby further reducing the Vo defect content in the channel and improving the performance stability of the TFT 2.

In a specific embodiment, the material of the oxygen supplementing layer 4 includes silicon oxide, and the material of the second passivation layer 5 includes silicon oxide.

For example, the oxygen supplement layer 4 is a silicon oxide film layer; the second passivation layer 5 is a silicon oxide film layer. Similar to the first passivation layer 3, although the second passivation layer 5 and the oxygen supplement layer 4 are made of the same material, the second passivation layer 5 and the oxygen supplement layer 4 have different film properties, such as the film refractive index, the purity of the silicon oxide material in the film, and the content of excess oxygen (exO) and N, H, _H2O , etc. in the film. For example:

Specifically, the refractive index of the second passivation layer 5 is greater than the refractive index of the oxygen supplementing layer 4 . Exemplarily, the refractive index of the second passivation layer 5 is greater than 1.45.

Specifically, compared with the second passivation layer 5 , the Si—O—Si stretching vibration peak in the oxygen supplementing layer 4 material moves toward the high wave number direction, has a narrower half-height width, and has a higher purity of the oxygen supplementing layer 4 material.

Specifically, the content of excess oxygen (exO) in the oxygen supplementing layer 4 is higher than that in the first passivation layer 3 , while the content of H, N, H ₂ O, etc. is much lower than that in the first passivation layer 3 .

In some embodiments, the oxygen diffusion performance of the first passivation layer 3 is better than that of the second passivation layer 5. Thus, the surplus oxygen in the oxygen supplementation layer 4 is more easily diffused to the TFT 2 through the first passivation layer 3, thereby reducing the Vo defect content in the channel region 20 and improving the performance stability of the TFT 2.

It should be noted that the first passivation layer and the second passivation layer can be made of not only silicon oxide material, but also silicon nitride material, or a composite material of silicon nitride and silicon oxide, etc., which can be determined according to actual needs and is not limited here. In addition, the material of the oxygen supplement layer is not limited to aluminum oxide or silicon oxide, but can also be other materials that can compensate for oxygen in the TFT channel and have very low content of N, H, and _H2O , which is not limited here.

In some embodiments, the ratio of the thickness of the first passivation layer 3 to the thickness of the oxygen supplement layer 4 may be 10-40; and the ratio of the thickness of the second passivation layer 5 to the thickness of the oxygen supplement layer 4 may be 20-40.

Exemplarily, the thickness of the oxygen supplementing layer 4 is greater than 10 nm. The thickness of the first passivation layer 3 is 100 nm-400 nm. The thickness of the second passivation layer 5 is 200 nm-400 nm.

An embodiment of the present application further provides a display panel, which includes any one of the display substrates described above, and may further include an opposite substrate.

Exemplarily, the display panel may be an LCD, the display substrate may be an array substrate, and the opposite substrate may be a color filter substrate.

Alternatively, the display panel may also be an OLED, the display substrate may be a driving backplane, and the opposite substrate may be a glass cover.

An embodiment of the present application further provides a display device, which includes the above-mentioned display panel.

Specifically, the display device can be applied to various electronic devices such as televisions, monitors, tablet computers, and smart phones.

In addition, based on the display substrate provided in the present application, the present application also provides a method for preparing the display substrate, as shown in FIG2 , the method comprises the following steps:

Step 101, as shown in FIG3, a thin film transistor 2 is prepared on a substrate 1;

Step 102, as shown in FIG3, preparing a first passivation layer 3 on the thin film transistor 2;

Step 103, as shown in Figure 4, prepare an oxygen supplement layer 4 on the first passivation layer 3, the oxygen supplement layer 4 at least covers the channel region 20 of the thin film transistor 2, the oxygen content in the oxygen supplement layer 4 is greater than the oxygen content in the first passivation layer 3, and the contents of hydrogen, nitrogen and water molecules in the oxygen supplement layer 4 are respectively less than the contents of hydrogen, nitrogen and water molecules in the first passivation layer 3.

In some embodiments, step 101, preparing a thin film transistor on a substrate, may specifically include:

As shown in FIG. 3 , a gate electrode 21 , an active layer 22 , a source electrode 24 , and a drain electrode 23 are sequentially prepared on a base substrate 1 to form a thin film transistor 2 .

In some embodiments, step 102, preparing a first passivation layer on the thin film transistor, may specifically include:

The silicon oxide or silicon nitride film layer is deposited by plasma chemical vapor deposition (PECVD) process, and the PECVD power density is less than 0.25W/ ^cm2 ;

High temperature annealing is performed at a temperature above 300°C.

Specifically, as shown in FIG3 , the first passivation layer 3 is deposited at a relatively low power by PECVD, which can reduce damage to the channel region 20 of the TFT 2 and oxidation of the source 24 and drain 23 films. At the same time, the oxygen diffusion performance of the first passivation layer 3 prepared is also relatively good, which is beneficial to the diffusion of excess oxygen (exO) in the oxygen supplement layer 4 to the channel region 20 of the TFT 2.

In addition, after the first passivation layer 3 is formed, high temperature annealing is performed at a temperature above 300°C. Under this high temperature condition, N, H, and _H2O in the first passivation layer 3 can be released, so that the content of N, H, and _H2O in the film layer can be as small as possible. However, at the same time, the excess oxygen (exO) in the film layer may also be released. Therefore, an oxygen supplementation layer 4 is required to supplement oxygen to the channel region 20 of the TFT 2.

In some embodiments, step 103, preparing an oxygen supplementing layer on the first passivation layer, may specifically include:

Using semiconductors, metals, semiconductor oxides or metal oxides as target materials, introducing a gas with an oxygen content greater than 50%, controlling the temperature of the film-forming substrate at greater than 100°C, and preparing an oxide film layer by magnetron sputtering.

For example, the target material may include Si, Al, SiO _x , AlO _x , etc. The thickness of the formed oxide film layer may be greater than 10 nm.

As shown in FIG4 , the magnetron sputtering process is used for oxygen-enriched film formation, and the oxygen replenishing layer 4 finally formed will contain a large amount of excess oxygen (exO) and a very small amount of N, H, and H ₂ O. In addition, during the preparation process, part of the excess oxygen (exO) will enter the channel region 20 of TFT2 under the action of plasma and temperature to replenish oxygen in the channel region 20 of TFT2, thereby reducing the Vo defect content in the channel region 20.

In some embodiments, after step 103, that is, after the oxygen supplement layer is prepared on the first passivation layer, the following steps may also be included:

As shown in FIG5 , a silicon oxide or silicon nitride film layer is deposited by a PECVD process to form a second passivation layer 5 , and the film forming temperature of the silicon oxide or silicon nitride film layer is greater than 300° C.

As shown in FIG. 5 , forming the second passivation layer 5 at a high temperature greater than 300° C. can promote the further diffusion of excess oxygen (exO) in the oxygen supplement layer 4 into the channel region 20 of the TFT 2, thereby further reducing the Vo defect content in the channel region 20 and improving the performance stability of the TFT 2.

Exemplarily, the overall process of the method for preparing a display substrate provided in an embodiment of the present application may roughly include: as shown in Figure 1, a gate (Gate) 21, a gate insulating layer (GI) 6, an active layer (Active) 22, a metal source electrode 24 and a drain electrode (SD) 23 are sequentially prepared on a base substrate 1 - a first passivation layer 3 is prepared - an oxygen supplement layer 4 is prepared - a second passivation layer 5 is prepared - a pixel electrode 7 is prepared.

Specifically, the active layer can be made of oxide semiconductor, such as indium gallium zinc oxide (IGZO); the gate electrode material can be made of common metal materials such as Al, Cu, Au, Ag, Ti, Ta, etc.; to prevent the SD electrode etching solution from damaging the oxide semiconductor active layer, the SD electrode can be made of a multi-layer composite structure, such as Mo/Cu/Mo, MoNb/Cu/MoNb, etc. Of course, the above materials are only examples, and the materials of each layer are not limited thereto, and can be determined according to actual needs.

It should be noted that in some embodiments of the present disclosure, the method for preparing the display substrate may further include more steps, which may be determined according to actual needs, and the embodiments of the present disclosure are not limited thereto. The detailed description and technical effects thereof may refer to the description of the display substrate and the display panel above, which will not be repeated here. In addition, in the method for preparing the display substrate provided in the embodiments of the present disclosure, the specific process methods and preparation processes of steps 101, 102 and 103 are not limited to the above embodiments, and may also be prepared by other process methods and steps, and the specific descriptions may refer to the description of each layer structure in the display substrate above, which will not be repeated here.

Obviously, those skilled in the art can make various changes and modifications to the embodiments of the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims (15)

1. A display substrate, comprising: substrate substrate; A thin film transistor is located on the substrate; A first passivation layer is located on a side of the thin film transistor away from the substrate; The oxygen supplement layer is located on the side of the first passivation layer away from the substrate, and at least covers the channel region of the thin film transistor. The oxygen content in the oxygen supplement layer is greater than the oxygen content in the first passivation layer, and the contents of hydrogen, nitrogen and water molecules in the oxygen supplement layer are respectively less than the contents of hydrogen, nitrogen and water molecules in the first passivation layer. 2 . The display substrate of claim 1 , wherein an orthographic projection pattern of the oxygen supplementing layer on the base substrate is the same as an orthographic projection pattern of the first passivation layer on the base substrate. The display substrate according to claim 1 , wherein a material of the oxygen supplementing layer comprises aluminum oxide. The display substrate of claim 1 , wherein a material of the oxygen supplementing layer comprises silicon oxide. 5 . The display substrate of claim 4 , wherein a material of the first passivation layer comprises silicon oxide, and a refractive index of the first passivation layer is greater than a refractive index of the oxygen supplementing layer. 6. The display substrate as described in claim 1, further comprising a second passivation layer, located on the side of the oxygen supplement layer away from the base substrate; the oxygen content in the oxygen supplement layer is greater than the oxygen content in the second passivation layer, and the contents of hydrogen, nitrogen and water molecules in the oxygen supplement layer are respectively less than the contents of hydrogen, nitrogen and water molecules in the second passivation layer. 7 . The display substrate according to claim 6 , wherein a material of the oxygen supplementation layer comprises silicon oxide; a material of the second passivation layer comprises silicon oxide, and a refractive index of the second passivation layer is greater than a refractive index of the oxygen supplementation layer. 8 . The display substrate of claim 6 , wherein the first passivation layer has better oxygen diffusion performance than the second passivation layer. 9 . The display substrate according to claim 6 , wherein a ratio of a thickness of the first passivation layer to a thickness of the oxygen supplementing layer is 10-40; and a ratio of a thickness of the second passivation layer to a thickness of the oxygen supplementing layer is 20-40. 10. A display panel, comprising the display substrate according to any one of claims 1 to 9. 11. A method for preparing a display substrate, comprising the following steps: preparing a thin film transistor on a substrate; preparing a first passivation layer on the thin film transistor; An oxygen supplement layer is prepared on the first passivation layer, the oxygen supplement layer at least covers the channel region of the thin film transistor, the oxygen content in the oxygen supplement layer is greater than the oxygen content in the first passivation layer, and the contents of hydrogen, nitrogen and water molecules in the oxygen supplement layer are respectively less than the contents of hydrogen, nitrogen and water molecules in the first passivation layer. 12. The preparation method according to claim 11, wherein preparing a first passivation layer on the thin film transistor specifically comprises: The silicon oxide or silicon nitride film layer is deposited by PECVD process, and the PECVD power density is less than 0.25W/ ^cm2 ; High temperature annealing is performed at a temperature above 300°C. 13. The preparation method according to claim 11, wherein preparing an oxygen supplementing layer on the first passivation layer specifically comprises: Using semiconductors, metals, semiconductor oxides or metal oxides as target materials, introducing a gas with an oxygen content greater than 50%, controlling the temperature of the film-forming substrate at greater than 100°C, and preparing an oxide film layer by magnetron sputtering. The preparation method according to claim 13 , wherein the target material comprises Si, Al, SiO _x , or AlO _x . 15. The preparation method according to any one of claims 11 to 14, wherein after preparing the oxygen supplement layer on the first passivation layer, the method further comprises: A silicon oxide or silicon nitride film layer is deposited by a PECVD process to prepare a second passivation layer, wherein the film forming temperature of the silicon oxide or silicon nitride film layer is greater than 300°C.