Display panel, manufacturing method thereof, and display device

Abstract

An embodiment of the present invention discloses a display panel, a manufacturing method thereof, and a display device. In a specific embodiment, the display panel includes: a substrate; and a reflective electrode formed on the substrate, wherein the reflective electrode includes a first reflective electrode layer, a second reflective electrode layer, and a third reflective electrode layer sequentially stacked on the substrate, and the sidewall of the second reflective electrode layer is not covered by the third reflective electrode layer. This embodiment utilizes the reflective electrode pattern formed by fracture. The sidewall of the second reflective electrode layer in the reflective electrode is not covered by the third reflective electrode layer, the manufacturing method is simple, suitable for micro display devices, and has broad application prospects.

Description

Technical Field

[0001] The present invention relates to the field of display technologies. More specifically, it relates to a display panel, a manufacturing method thereof, and a display device. Background Art

[0002] In recent years, silicon-based OLED micro-displays have been widely used as near-eye displays in the VR and AR fields. Aluminum (Al) is mostly used as the reflective layer material. However, the reflectivity of the Al material as the anode reflective layer is usually only 70% - 88%, which is difficult to meet the performance requirements of high brightness and low power consumption of current products.

[0003] Silver (Ag), as the metal material with the highest reflectivity, has a reflectivity as high as 99%, which can greatly improve the product performance of micro-displays. Therefore, it is urgent to develop a structure with Ag as the reflective layer. However, the patterning method of conventional Al reflective electrodes cannot be applied to Ag materials. At present, the patterning method applied to Al materials cannot be directly applied to Ag materials. Therefore, a manufacturing method for the reflective electrode of Ag materials applicable to micro-displays is needed. Summary of the Invention

[0004] The purpose of the present invention is to provide one, so as to solve at least one of the problems existing in the prior art.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions:

[0006] The first aspect of the present invention provides a display panel, including:

[0007] A substrate; and

[0008] A reflective electrode formed on the substrate,

[0009] wherein the reflective electrode includes a first reflective electrode layer, a second reflective electrode layer, and a third reflective electrode layer stacked on the substrate in sequence, and the sidewall of the second reflective electrode layer is not covered by the third reflective electrode layer.

[0010] In some optional embodiments,

[0011] wherein the sidewall of the first reflective electrode protrudes from the sidewall of the second reflective electrode and the sidewall of the third reflective electrode protrudes from the sidewall of the second reflective electrode.

[0012] In some optional embodiments,

[0013] The length that the sidewall of the first reflective electrode protrudes from the sidewall of the second reflective electrode is: greater than or equal to 0.1 times the thickness of the second reflective electrode and less than or equal to 1 time the thickness of the second reflective electrode.

[0014] In some alternative embodiments, the display panel further includes: a first undercut portion that surrounds the reflective electrode,

[0015] The thickness of the first undercut portion is greater than the thickness of the reflective electrode, and there is a gap between the orthographic projection of the reflective electrode on the substrate and the orthographic projection of the first undercut portion on the substrate.

[0016] A second aspect of the present invention provides a display device including the display panel described above.

[0017] A third aspect of the present invention provides a method for manufacturing a display panel, including:

[0018] Forming a first inorganic material layer on the substrate and a second inorganic material layer covering the first inorganic material layer;

[0019] Patterning the second inorganic material layer to form a second undercut portion and patterning the first inorganic material layer to form a first undercut portion, the orthographic projection of the second undercut portion on the substrate covers the orthographic projection of the first undercut portion on the substrate and the area of the orthographic projection of the second undercut portion on the substrate is larger than the area of the orthographic projection of the first undercut portion on the substrate;

[0020] Forming a reflective electrode material layer on the second undercut portion, the reflective electrode material layer includes a first sub - portion and a second sub - portion, the first sub - portion covers the substrate exposed by the opening defined by the second undercut portion, and the second sub - portion covers the second undercut portion;

[0021] Forming a filling layer on the reflective electrode material layer, the filling layer fills the openings defined by the first undercut portion and the second undercut portion;

[0022] Removing the second undercut portion and at least part of the filling layer to expose at least part of the first sub - portion to obtain the reflective electrode of the display panel.

[0023] In some alternative embodiments, patterning the second inorganic material layer to form a second undercut portion and patterning the first inorganic material layer to form a first undercut portion further includes:

[0024] Patterning the second inorganic material layer to form a second undercut portion by dry etching and patterning the first inorganic material layer to form a first undercut portion by dry etching,

[0025] wherein the etching rate of the first inorganic material layer is greater than the etching rate of the second inorganic material layer.

[0026] In some alternative embodiments, the thickness of the first undercut portion is greater than the thickness of the reflective material layer, and the material of the first undercut portion is different from the material of the second undercut portion,

[0027] Removing the second undercut portion and at least part of the filling layer to expose at least part of the first sub - portion, to obtain the reflective electrode of the display panel further includes:

[0028] Removing the second sub - portion, the second undercut portion and part of the filling layer by chemical - mechanical planarization method until the first undercut portion is exposed;

[0029] Coating and patterning photoresist on the first undercut portion;

[0030] Forming an opening in the filling layer based on the patterned photoresist to expose at least part of the first sub - portion, to obtain the reflective electrode of the display panel.

[0031] In some alternative embodiments, the material of the filling layer is photoresist.

[0032] Removing the second undercut portion and at least part of the filling layer to expose at least part of the first sub - portion, to obtain the reflective electrode of the display panel further includes:

[0033] Ashing the filling layer to expose the second sub - portion;

[0034] Wet - etching to remove the second sub - portion;

[0035] Removing the ashed filling layer, the second sub - portion and the second undercut portion to obtain the reflective electrode of the display panel.

[0036] In some alternative embodiments, before forming the first inorganic material layer and the second inorganic material layer covering the first inorganic material layer on the substrate, the manufacturing method further includes:

[0037] Forming a contact layer on the substrate.

[0038] Wherein, the orthographic projection of the contact layer on the substrate covers the orthographic projection of the reflective electrode on the substrate, and the material of the contact layer is titanium nitride.

[0039] In some alternative embodiments, forming the filling layer on the reflective electrode material layer further includes:

[0040] Forming the filling layer on the reflective electrode material layer by high - density plasma deposition method.

[0041] In some alternative embodiments, forming the reflective electrode material layer on the second undercut portion further includes:

[0042] Sequentially forming a first reflective electrode material layer, a second reflective electrode material layer and a third reflective electrode material layer on the second undercut portion.

[0043] The materials of the first reflective electrode material layer and the third reflective electrode material layer are indium tin oxide, and the material of the second reflective electrode material layer is silver.

[0044] In some alternative embodiments, the reflective electrode is an anode.

[0045] The beneficial effects of the present invention are as follows:

[0046] In view of the existing problems, the present invention provides a display panel, a manufacturing method thereof, and a display device. By forming a first undercut portion and a second undercut portion on a substrate to form an undercut structure, the orthographic projection of the second undercut portion on the substrate covers the orthographic projection of the first undercut portion on the substrate and the area of the orthographic projection of the second undercut portion on the substrate is larger than that of the first undercut portion on the substrate, so that the reflective material layer breaks to form a reflective electrode pattern by virtue of the undercut structure, with high patterning accuracy and capable of meeting the accuracy requirements of a microdisplay. At the same time, this method does not require dry etching of the reflective electrode material layer, and the reflective electrode film has a high reflectivity, without problems such as particles, etching rate, and scratches, improving the product performance and yield, and having a wide application prospect. Description of the Drawings

[0047] The following further elaborates on the specific embodiments of the present invention with reference to the drawings.

[0048] Figure 1 The flowchart of the manufacturing method of the display panel showing an embodiment of the present application.

[0049] Figures 2 - 8 The cross-sectional structure diagrams corresponding to the main steps of the manufacturing process of the display panel showing an embodiment of the present application.

[0050] Figures 9 - 14 The cross-sectional structure diagrams corresponding to the main steps of the manufacturing process of the display panel showing another embodiment of the present application. Detailed Description of the Embodiments

[0051] To more clearly illustrate the present invention, the following further describes the present invention with reference to the embodiments and the drawings. Similar components in the drawings are denoted by the same or similar reference numerals. Those skilled in the art should understand that the content specifically described below is illustrative rather than restrictive, and should not limit the protection scope of the present invention.

[0052] It should be noted that the terms "having", "comprising", "including", etc. described in the present invention have an open meaning, that is, when describing that a module "has", "comprises", or "includes" a first element, a second element, and / or a third element, it means that the module includes other elements in addition to the first element, the second element, and / or the third element. In addition, the ordinal numbers such as "first", "second", and "third" in the present invention are not intended to limit the specific order, but only to distinguish each part.

[0053] As used in the present invention, the terms "on...", "formed on...", and "disposed on..." may mean that one layer is directly formed or disposed on another layer, or may mean that one layer is indirectly formed or disposed on another layer, i.e., there are other layers between the two layers.

[0054] In addition, in the present invention, the term "co-layer setting" means that two layers, components, members, elements or parts can be formed by the same preparation process (such as a patterning process, etc.), and generally, these two layers, components, members, elements or parts are formed of the same material. For example, the co-layer setting of two or more functional layers means that these co-layered functional layers can be formed by using the same material layer and the same preparation process, thereby simplifying the preparation process of the display substrate.

[0055] In the prior art, the conventional patterning process of the Al material reflective electrode is: (1) coating, (2) lithography, (3) dry etching. However, the non-volatile by-products generated during the dry etching of the Ag material will cause problems such as particle issues and unstable etching rates. In current display products, there is an improved patterning process for the Ag material: (1) lithography, (2) coating, (3) lift-off, but this solution has many limitations. For example, volatile lithography materials are difficult to enter a high-vacuum coating equipment, making it difficult to obtain a high-reflectivity Ag thin film. The insolubility of the Ag material in the lift-off solution results in frequent particle and scratch problems. However, if wet etching is used to pattern the Ag material, the accuracy is only 20 to 30 μm, which cannot meet the accuracy requirements of 2 to 3 μm for microdisplays. Therefore, it is difficult to implement the patterning of the Ag material using the conventional process flow, and the prior art cannot achieve the application of the Ag material reflective electrode in the mass production stage in the field of microdisplays.

[0056] Based on one of the above problems, with reference to Figure 1 as shown, an embodiment of the present invention provides a method for manufacturing a display panel, including:

[0057] S1. Form a first inorganic material layer on a substrate and a second inorganic material layer covering the first inorganic material layer;

[0058] S2. Pattern the second inorganic material layer to form a second undercut portion, and pattern the first inorganic material layer to form a first undercut portion. The orthographic projection of the second undercut portion on the substrate covers the orthographic projection of the first undercut portion on the substrate and the area of the orthographic projection of the second undercut portion on the substrate is larger than the area of the orthographic projection of the first undercut portion on the substrate;

[0059] S3. Form a reflective electrode material layer on the second undercut portion. The reflective electrode material layer includes a first sub-portion and a second sub-portion. The first sub-portion covers the substrate exposed by the opening defined by the second undercut portion, and the second sub-portion covers the second undercut portion;

[0060] S4. Form a filling layer on the reflective electrode material layer, and the filling layer fills the opening defined by the first undercut portion and the second undercut portion;

[0061] S5. Remove the second undercut portion and at least part of the filling layer to expose at least part of the first sub - portion, so as to obtain the reflective electrode of the display panel.

[0062] In this embodiment, by forming an undercut structure during the process of forming the first undercut portion and the second undercut portion on the substrate, the orthographic projection of the second undercut portion on the substrate covers the orthographic projection of the first undercut portion on the substrate and the area of the orthographic projection of the second undercut portion on the substrate is larger than the area of the orthographic projection of the first undercut portion on the substrate, so that the reflective material layer forms a reflective electrode pattern by breaking with the help of this undercut structure, with high patterning accuracy and capable of meeting the accuracy requirements of the micro - display; meanwhile, this method does not require dry etching of the reflective electrode material layer, the reflective electrode film has a high reflectivity, and there are no problems such as particles, etching rate, and scratches, improving the product performance and yield, and having a wide application prospect.

[0063] It should be noted that the reflective electrode of the display panel fabricated in the embodiment of the present invention is the electrode relative to the organic light - emitting layer and away from the light - emitting side of the display panel in an OLED (Organic Light Emitting Diode) display panel, and is used to reflect ambient light and improve the light - emitting efficiency. Currently, most of the organic light - emitting diodes in common display panels are top - emission devices and have a common - cathode structure, that is, the overall structure of the display panel is to stack a driving circuit layer, an anode, an organic light - emitting layer, and a cathode on a substrate. In a display panel with such a structure, the reflective electrode is the anode disposed between the driving circuit layer and the organic light - emitting layer.

[0064] Those skilled in the art should understand that the present application is not limited to this. The organic light - emitting diode of the display panel fabricated in the embodiment of the present application can also be a bottom - emission device and have a common - cathode structure. Then the overall structure of the display panel is to stack a driving circuit layer, a cathode, an organic light - emitting layer, and an anode on a transparent substrate, and the substrate is the light - emitting side. At this time, the reflective electrode is the patterned anode of the organic light - emitting layer away from the light - emitting side; of course, if a display panel with a patterned cathode as the reflective electrode is satisfied, for a top - emission device, the reflective electrode can also be the cathode disposed between the driving circuit layer and the organic light - emitting layer, and for a bottom - emission device, the reflective electrode is the patterned cathode of the organic light - emitting layer away from the light - emitting side.

[0065] For the sake of convenience of description, hereinafter, the case where the reflective electrode is the anode disposed between the driving circuit layer and the organic light - emitting layer will be taken as an example for illustration. The following refers to Figures 2 through 8 a specific example to describe the process flow of the manufacturing method of the display panel.

[0066] Refer to Figure 2As shown, before step S1, a driving circuit layer 110 is formed on the substrate 100. The driving circuit layer 110 includes thin film transistors for driving organic light emitting diodes.

[0067] A plurality of tungsten vias 111 for transmitting electrical signals may be provided in the driving circuit layer 110 to transmit the signals of the electrodes in the thin film transistors in the driving circuit layer 110 to the reflective electrode to be formed.

[0068] In this case, preferably, before step S1, it further includes: forming a contact layer 120 on the substrate 100, wherein the orthographic projection of the contact layer 120 on the substrate 100 covers the orthographic projection of the reflective electrode to be formed on the substrate, and the material of the contact layer 120 is titanium nitride (TiN). Of course, those skilled in the art should understand that since the driving circuit layer 110 has been formed on the substrate 100, referring to Figure 2 As shown, the contact layer 120 is substantially also formed on the driving circuit layer 110.

[0069] The reason for such a setting is that usually Ag is used as the reflective electrode, and its texture is soft and usually requires an additional metal oxide layer with a more stable interface, such as indium tin oxide (ITO), as a protective layer. However, the contact interface between indium tin oxide and tungsten in the tungsten via is not good, and there may be a risk of different signals in a small-sized display panel. By providing the contact layer 120 of titanium nitride, the lap advantage of titanium and tungsten can be utilized to form a good contact interface, improve the signal transfer effect, and thus improve the yield of the display panel.

[0070] Referring to Figure 3 As shown, in step S1, a first inorganic material layer 131 and a second inorganic material layer 141 covering the first inorganic material layer 131 are formed on the substrate 100.

[0071] Specifically, when the contact layer 120 is pre-formed, the first inorganic material layer 131 can be formed on the contact layer 120 by chemical vapor deposition (CVD), and the second inorganic material layer 141 is also formed on the first inorganic material layer 131 by chemical vapor deposition. The material of the first inorganic material layer 131 can be silicon nitride (SiNx), and the material of the second inorganic material layer can be silicon oxide (SiOx).

[0072] It should be noted that the present application does not aim to limit the specific materials of the first inorganic material layer 131 and the second inorganic material layer 141, as long as they are inorganic materials with different materials, so as to facilitate the material selection in the subsequent patterning and removal steps. The specific content will be described below and will not be elaborated here.

[0073] In addition, it should be noted that in this example, the thickness of the first inorganic material layer 131 should be greater than the thickness of the reflective electrode to be formed. That is, preferably, the thickness of the first inorganic material layer 131 is greater than the thickness of the reflective material layer to be formed. For example, the thickness of the first inorganic material layer 131 can be twice the thickness of the reflective material layer. In other words, the thickness of the first undercut portion 130 formed subsequently should be greater than the thickness of the reflective electrode material layer. Through this setting, the surface of the reflective electrode can be protected from being damaged in the subsequent removal step. The specific content will be described below and will not be elaborated here.

[0074] Referring Figure 4 As shown, in step S2, the second inorganic material layer 141 is patterned to form the second undercut portion 140, and the first inorganic material layer 131 is patterned to form the first undercut portion 130. The orthographic projection of the second undercut portion 140 on the substrate 100 covers the orthographic projection of the first undercut portion 130 on the substrate 100, and the area of the orthographic projection of the second undercut portion 140 on the substrate 100 is greater than the area of the orthographic projection of the first undercut portion 130 on the substrate 100.

[0075] Specifically, because the materials of the first inorganic material layer 131 and the second inorganic material layer 141 are different, by selecting the etching selectivity of dry etching, the second inorganic material layer 141 and the first inorganic material layer 131 are successively dry-etched to form the second undercut portion 140 and the first undercut portion 130. Among them, the etching rate of the first inorganic material layer 131 is greater than the etching rate of the second inorganic material layer 141, so that the side wall of the first undercut portion 130 is located within the second undercut portion 140, that is, the orthographic projection of the second undercut portion 140 on the substrate 100 covers the orthographic projection of the first undercut portion 130 on the substrate 100 and the area of the orthographic projection of the second undercut portion 140 on the substrate 100 is greater than the area of the orthographic projection of the first undercut portion 130 on the substrate 100, forming an undercut structure.

[0076] More preferably, when the material of the first inorganic material layer 131 is silicon nitride (SiNx) and the material of the second inorganic material layer 141 is silicon oxide (SiOx), the etching rate of dry etching satisfies that the ratio of the etching rate of the first inorganic material layer 131 to the etching rate of the second inorganic material layer 141 is greater than or equal to 5. More preferably, the ratio of the etching rate of the first inorganic material layer 131 to the etching rate of the second inorganic material layer 141 is 5, 7 or 20.

[0077] Of course, the materials of the first inorganic material layer 131 and the second inorganic material layer 141 can be replaced with other materials with better TGA parameters, such as silicone / silicon nitride, silicone / silicon oxide, etc., which will not be elaborated here.

[0078] Of course, the method for forming the first undercut portion 130 and the second undercut portion 140 is not limited to dry etching. It is also possible to first use dry etching to etch an opening in the second inorganic material layer 141, and then use wet etching to form the Figure 4 first undercut portion 130 and the second undercut portion 140 as shown.

[0079] With this arrangement, by using the first inorganic material layer and the second inorganic material layer of different materials, it is only necessary to reasonably set the etching selectivity to form an undercut structure composed of the first undercut portion and the second undercut portion, and the method is simple.

[0080] Referring to Figure 5 as shown, in step S3, a reflective electrode material layer 150 is formed on the second undercut portion 140. The reflective electrode material layer includes a first sub-portion and a second sub-portion. The first sub-portion covers the substrate 100 exposed by the opening defined by the second undercut portion, and the second sub-portion covers the second undercut portion 140.

[0081] Specifically, the reflective electrode material layer 150 is formed on the second undercut portion 140 by chemical vapor deposition. The reflective electrode material layer 150 can be formed by sputtering.

[0082] When the main material of the reflective electrode is Ag, the reflective electrode is preferably a multi-layer structure. For example, the reflective electrode can be a sandwich structure composed of ITO, Ag, and ITO. At this time, the step of forming the reflective electrode material layer 150 on the second undercut portion 140 further includes: sequentially forming a first reflective electrode material layer 151, a second reflective electrode material layer 152, and a third reflective electrode material layer 153 on the second undercut portion 140. The materials of the first reflective electrode material layer 151 and the third reflective electrode material layer 153 are ITO, and the material of the second reflective electrode material layer 152 is Ag.

[0083] With this arrangement, it is possible to use ITO with a stable interface to protect the soft Ag, and at the same time, the strong reflectivity of Ag can be used to improve the reflection performance of the reflective electrode to be formed; in addition, ITO can match the contact work function of the organic light-emitting layer, and ITO can simultaneously serve as the injection layer of the organic light-emitting diode, reducing the process difficulty and achieving multiple benefits.

[0084] Through this step, the undercut structure formed by the first undercut portion 130 and the second undercut portion 140 can be utilized to form a substrate on which the reflective electrode material layer 150 is naturally fractured during sputtering to expose the opening defined by the second undercut portion 140, and when the base layer 140 is formed on the substrate, it directly covers the surface of the contact layer 140. In the present application, by forming the undercut structure and then fracturing the reflective electrode material layer by using the structural characteristics of the undercut structure, it is equivalent to forming a damascene negative etching process structure. The first sub-portion of the reflective electrode material layer 150 directly forms the pattern of the reflective electrode to be formed. This process has high precision, and there is no direct etching step in the actual step of patterning the reflective electrode material layer, so there are no etching by-products, ensuring the film-forming effect of the Ag material layer; in addition, by using the undercut structure continuous coating process, the reflectivity of the Ag reflective electrode is generally greater than 99%, and there is no multiple process after Ag coating, thus reducing the problem of the decrease in reflectivity caused by the oxidation of Ag in subsequent processes.

[0085] Preferably, when the thickness of the reflective electrode material layer 150: the thickness of the first undercut portion 130: the thickness of the second undercut portion 140 is 1:2:8, this ratio can effectively prevent the reflective electrode material layer 150 from adhering at the opening of the undercut structure, so that the metal material of the reflective electrode material layer 150 can be effectively fractured by means of the first undercut portion 130 and the second undercut portion 140, thereby achieving the effect of patterning the reflective electrode material layer 150.

[0086] It should be noted that in the embodiments of the present application, since the three-layer reflective electrode material layer is continuously sputtered and each layer of the reflective electrode material layer is fractured by the undercut structure, compared with the three-layer reflective electrode formed by using multiple processes in the prior art, it is impossible to form a coating on the side walls between the layers. That is to say, the reflective electrode in the display panel of the embodiments of the present application has an obvious structural feature that the natural fracture cross-section will not form any coating, that is, the side wall of the second reflective electrode material layer located in the first sub-portion will not be coated by the side wall of the third reflective electrode material layer.

[0087] Refer to Figure 6 As shown, in step S4, a filling layer 160 is formed on the reflective electrode material layer 150, and the filling layer 160 fills the opening defined by the first undercut portion 130 and the second undercut portion 140.

[0088] Specifically, the material of the filling layer 160 can be an inorganic material, such as silicon oxide (SiOx). The filling layer 160 is intended to form positive protection for the first sub-portion where the reflective electrode is to be formed.

[0089] Preferably, the filling layer 160 can be formed on the reflective electrode material layer 150 by a high-density plasma deposition (HDP) method. The high-density plasma deposition method has excellent hole filling ability, so that the larger opening space defined by the first undercut 130 can be fully filled with the filling layer, ensuring effective protection for the first sub-part where the reflective electrode is to be formed.

[0090] In step S5, the second undercut and part of the filling layer are removed to expose at least part of the first sub-part, so as to obtain the reflective electrode of the display panel.

[0091] Specifically, referring to Figure 7 as shown, in this example, the second sub-part of the reflective electrode material layer 150, the second undercut 140, and part of the filling layer 160 are removed by a chemical mechanical polishing (CMP) method until the first undercut is exposed;

[0092] A photoresist is coated on the first undercut 130 and patterned;

[0093] Based on the patterned photoresist, an opening is formed in the filling layer 160 to expose at least part of the first sub-part, as Figure 8 shown, so as to obtain the reflective electrode of the display panel.

[0094] Precisely because the materials of the first undercut 130 and the second undercut 140 are different, the chemical mechanical polishing equipment can automatically stop above the first undercut after removing the second sub-part, the second undercut 140, and part of the filling layer 160 by controlling the mechanical polishing rate; precisely because the thickness of the first undercut 130 is greater than the thickness of the reflective electrode material layer 150, the surface of the reflective electrode material layer 150 will not be damaged when mechanical polishing is performed. In addition, the filling layer 160 can also play a protective role.

[0095] The reasonable cooperation of the above structures and parameters can significantly improve the manufacturing yield of the reflective electrode, thereby improving the yield of the display panel and having broad application prospects.

[0096] It should be noted that in this example, because of the different material characteristics of the first undercut and the second undercut, chemical mechanical polishing is used for planarization. Finally, the filling layer needs to be further patterned to form an opening to expose at least part of the first sub-part of the reflective electrode material layer. After the first sub-part is exposed, it is equivalent to completing the manufacturing process of the reflective electrode.

[0097] In the actual manufacturing process of the display panel, when the height of the first undercut portion permits, the first undercut portion and the remaining filling layer can directly serve as the pixel defining layer. It is only necessary to form an organic light-emitting layer in the opening and further form a light extraction electrode. Of course, when the height of the first undercut portion is insufficient to define a pixel, a pixel defining layer, an organic light-emitting layer, and a light extraction electrode can also be further formed, which will not be elaborated here.

[0098] In another alternative example, referring to Figure 9 as shown, a method different from the above example can be adopted for the steps after step S3. The above example's method is still used to fabricate the first undercut portion 130 and the second undercut portion 140 to form an undercut structure. Then, the reflective electrode material layer 150 is sputtered over the entire surface, and the undercut structure is used to break the reflective electrode material layer. As a result, the reflective electrode material layer 150 includes a first sub-portion and a second sub-portion. The first sub-portion covers the substrate exposed by the opening defined by the second undercut portion, and the second sub-portion covers the second undercut portion 140. Of course, if the contact layer 120 has been pre-formed, the first sub-portion directly covers the contact layer 120 exposed by the opening defined by the second undercut portion 140.

[0099] Next, referring to Figures 10 through 14 the subsequent manufacturing process of this example will be described.

[0100] Particularly, in step S4 of this example, the material of the filling layer 170 is photoresist. Then, referring to Figure 10 as shown, a filling layer 170 is formed on the reflective electrode material layer, and the filling layer 170 fills the openings defined by the first undercut portion 130 and the second undercut portion 40.

[0101] In step S5, the second undercut portion 140 and the filling layer 170 are removed to expose the first sub-portion, so as to obtain the reflective electrode of the display panel.

[0102] Specifically, referring to Figure 11 as shown, the filling layer 170 is ashed to expose the second sub-portion, obtaining the ashed filling layer 171.

[0103] Referring to Figure 12 as shown, the second sub-portion 140 is removed by wet etching. Subsequently, referring to Figure 13 as shown, the ashed filling layer 171, the second sub-portion, and the second undercut portion 140 are removed to obtain the reflective electrode of the display panel.

[0104] Specifically, by debugging the dry etching process, the ratio, pressure, and power of the C / H / F gas are adjusted to adapt the selection ratio of the photoresist material and silicon oxide (SiO) to be close to 1:1, thereby removing the ashed filling layer 171, the second sub-portion, and the second undercut portion 140.

[0105] After that, referring toFigure 14 As shown, by further removing the first undercut portion 130, a reflective electrode is obtained.

[0106] It should be noted that in this example, since a photoresist is used as the material of the filling layer and the remaining photoresist is completely removed finally, and there is a gap between the first undercut portion 130 and the reflective electrode, therefore, in this example, the first undercut portion 130 is useless for the subsequent structure and also needs to be removed.

[0107] Of course, the present application does not limit the order of finally removing the ashed filling layer, the second undercut portion and the first undercut portion. It is also possible to reasonably select the ratio, pressure and power of C / H / F gas to adapt to the selection ratio of the photoresist material and silicon oxide (SiO), and remove them together at one time, which will not be elaborated here.

[0108] Based on the same inventive concept, an embodiment of the present invention further provides a display panel, including the display panel manufactured in the above embodiment.

[0109] The display panel includes: a substrate; and a reflective electrode formed on the substrate.

[0110] Wherein, the reflective electrode includes a first reflective electrode layer, a second reflective electrode layer and a third reflective electrode layer stacked on the substrate in sequence, and the side wall of the second reflective electrode layer is not covered by the third reflective electrode layer.

[0111] For the reflective electrode with a sandwich structure manufactured by this method, because of the undercut structure continuous coating process, the reflectivity of the reflective motor is generally greater than 99%, and there is no multiple process after Ag coating, thus reducing the problem of the decrease in reflectivity caused by the oxidation of Ag in the subsequent process. Therefore, the formed ITO / Ag / ITO has the remarkable structural feature of a flat cross section. There is no ITO coating phenomenon caused by multiple processes in ITO, nor the Profile flat phenomenon caused by normal ITO / Ag / ITO Dry Etch.

[0112] However, it should also be noted that due to the difference in the metal ductility of Ag and ITO, in the actually manufactured display panel products, the three-layer structure of the reflective electrode has a slightly undercut morphology feature, that is, the sides of the first reflective electrode and the third reflective electrode slightly protrude from the side of the second reflective electrode, that is, the side walls of the first reflective electrode, the second reflective electrode and the third reflective electrode are not flush.

[0113] Specifically, in some optional embodiments, as Figure 8 shown, the side wall of the first reflective electrode protrudes from the side wall of the second reflective electrode and the side wall of the third reflective electrode protrudes from the side wall of the second reflective electrode.

[0114] Optionally, the length by which the side wall of the first reflective electrode protrudes from the side wall of the second reflective electrode is: greater than or equal to 0.1 times the thickness of the second reflective electrode and less than or equal to 1 time the thickness of the second reflective electrode.

[0115] Further optionally, when an embodiment is fabricated through the Figures 2 through 8 process shown, a first undercut portion 130 is retained in the display panel. In this case, the display panel has a more specific structural feature of fabricating a reflective electrode using the undercut structure in the embodiments of the present application. Specifically, as Figure 8 shown, the display panel further includes: a first undercut portion 130, the first undercut portion 130 surrounding the reflective electrode,

[0116] the thickness of the first undercut portion is greater than the thickness of the reflective electrode, and the orthographic projection of the reflective electrode on the substrate and the orthographic projection of the first undercut portion on the substrate have a gap.

[0117] In summary, for the display panel fabricated in the embodiments of the present application, the reflective electrode does not have the ITO coating phenomenon caused by multiple processes of the reflective electrode compared with the prior art, nor does it conform to the side alignment phenomenon caused by the conventional ITO / Ag / ITO dry etching. In addition, in some embodiments, it does not have the structural feature of having a gap and surrounding the reflective electrode with a first undercut portion whose height is greater than the reflective electrode.

[0118] Based on the same inventive concept, an embodiment of the present invention further provides a display device, including the display panel described in the above embodiments.

[0119] Since the display panel included in the display device provided in the embodiments of the present application corresponds to the display panels provided in the above several embodiments, the previous implementation manners are also applicable to this embodiment and will not be described in detail in this embodiment.

[0120] In this embodiment, the display device can be a VR or AR near-eye microdisplay, as well as other application scenarios of microdisplays, especially in application fields with high requirements for the reflectivity of the reflective electrode and extremely small pixel sizes of the display, and has good product yield and stability.

[0121] In view of the existing problems at present, the present invention provides a display panel, a manufacturing method thereof, and a display device. By forming an undercut structure during the process of forming a first undercut portion and a second undercut portion on a substrate, the orthographic projection of the second undercut portion on the substrate covers the orthographic projection of the first undercut portion on the substrate and the area of the orthographic projection of the second undercut portion on the substrate is larger than the area of the orthographic projection of the first undercut portion on the substrate, so that the reflective material layer is broken by means of the undercut structure to form a reflective electrode pattern, with high patterning accuracy and capable of meeting the accuracy requirements of a microdisplay; at the same time, this method does not require dry etching of the reflective electrode material layer, the reflective electrode film has a high reflectivity, and there are no problems such as particles, etching rate, and scratches, improving the product performance and yield, and having a wide application prospect.

[0122] Obviously, the above-mentioned embodiments of the present invention are merely examples for clearly illustrating the present invention, rather than limitations on the implementation manners of the present invention. For those of ordinary skill in the art, other different forms of changes or variations can be made on the basis of the above description. It is impossible to enumerate all the implementation manners here. Any obvious changes or variations derived from the technical solutions of the present invention still fall within the protection scope of the present invention.

Claims

1. A display panel, characterized in that, Comprising: a substrate; and a reflective electrode formed on the substrate, wherein the reflective electrode includes a first reflective electrode layer, a second reflective electrode layer, and a third reflective electrode layer that are sequentially stacked on the substrate, and sidewalls of the second reflective electrode layer are not covered by the third reflective electrode layer, the reflective electrode is formed by the following steps: forming a first inorganic material layer on the substrate and a second inorganic material layer covering the first inorganic material layer; patterning the second inorganic material layer to form a second undercut portion, and patterning the first inorganic material layer to form a first undercut portion, a positive projection of the second undercut portion on the substrate covers a positive projection of the first undercut portion on the substrate and a positive projection area of the second undercut portion on the substrate is larger than a positive projection area of the first undercut portion on the substrate; forming a reflective electrode material layer on the second undercut portion, the reflective electrode material layer includes a first sub-portion and a second sub-portion, the first sub-portion covers the substrate exposed by an opening defined by the second undercut portion, and the second sub-portion covers the second undercut portion; forming a filling layer on the reflective electrode material layer, the filling layer fills openings defined by the first undercut portion and the second undercut portion; removing the second undercut portion and at least part of the filling layer to expose at least part of the first sub-portion to obtain the reflective electrode.

2. The display panel according to claim 1, characterized in that, wherein, Sidewalls of the first reflective electrode protrude from sidewalls of the second reflective electrode and sidewalls of the third reflective electrode protrude from sidewalls of the second reflective electrode.

3. The display panel according to claim 2, characterized in that, A length that sidewalls of the first reflective electrode protrude from sidewalls of the second reflective electrode is: greater than or equal to 0.1 times a thickness of the second reflective electrode and less than or equal to 1 time the thickness of the second reflective electrode.

4. The display panel according to claim 1, characterized in that, Further comprising: the first undercut portion, the first undercut portion surrounds the reflective electrode, a thickness of the first undercut portion is greater than a thickness of the reflective electrode, and a positive projection of the reflective electrode on the substrate and a positive projection of the first undercut portion on the substrate have a gap.

5. A display device, characterized in that, A display panel according to any one of claims 1-4.

6. A method for manufacturing a display panel, characterized in that, Comprising: forming a first inorganic material layer on a substrate and a second inorganic material layer covering the first inorganic material layer; patterning the second inorganic material layer to form a second undercut portion, and patterning the first inorganic material layer to form a first undercut portion, a positive projection of the second undercut portion on the substrate covers a positive projection of the first undercut portion on the substrate and a positive projection area of the second undercut portion on the substrate is larger than a positive projection area of the first undercut portion on the substrate; forming a reflective electrode material layer on the second undercut portion, the reflective electrode material layer includes a first sub-portion and a second sub-portion, the first sub-portion covers the substrate exposed by an opening defined by the second undercut portion, and the second sub-portion covers the second undercut portion; forming a filling layer on the reflective electrode material layer, the filling layer fills openings defined by the first undercut portion and the second undercut portion; Remove the second undercut portion and at least part of the filling layer to expose at least part of the first sub - portion, so as to obtain the reflective electrode of the display panel.

7. The manufacturing method according to claim 6, characterized in that, The patterning of the second inorganic material layer to form the second undercut portion and the patterning of the first inorganic material layer to form the first undercut portion further include: Patterning the second inorganic material layer to form the second undercut portion by dry etching and patterning the first inorganic material layer to form the first undercut portion by dry etching, wherein the etching rate of the first inorganic material layer is greater than that of the second inorganic material layer.

8. The manufacturing method according to claim 6, characterized in that, The thickness of the first undercut portion is greater than the thickness of the reflective electrode material layer, and the material of the first undercut portion is different from that of the second undercut portion. The removing of the second undercut portion and at least part of the filling layer to expose at least part of the first sub - portion, so as to obtain the reflective electrode of the display panel further includes: Removing the second sub - portion, the second undercut portion and part of the filling layer by chemical mechanical planarization method until the first undercut portion is exposed; Coating and patterning photoresist on the first undercut portion; Forming an opening in the filling layer based on the patterned photoresist to expose at least part of the first sub - portion, so as to obtain the reflective electrode of the display panel.

9. The manufacturing method according to claim 6, characterized in that,The material of the filling layer is photoresist. The removing of the second undercut portion and at least part of the filling layer to expose at least part of the first sub - portion, so as to obtain the reflective electrode of the display panel further includes: Ashing the filling layer to expose the second sub - portion; Wet etching to remove the second sub - portion; Removing the ashed filling layer, the second sub - portion and the second undercut portion to obtain the reflective electrode of the display panel.

10. The manufacturing method according to claim 6, characterized in that, Before forming the first inorganic material layer and the second inorganic material layer covering the first inorganic material layer on the substrate, the manufacturing method further includes: Forming a contact layer on the substrate, wherein the orthographic projection of the contact layer on the substrate covers the orthographic projection of the reflective electrode on the substrate, and the material of the contact layer is titanium nitride.

11. The manufacturing method according to claim 6, characterized in that, The forming of the filling layer on the reflective electrode material layer further includes: Forming a filling layer on the reflective electrode material layer by high - density plasma deposition method.

12. The manufacturing method according to claim 6, characterized in that, The forming of the reflective electrode material layer on the second undercut portion further includes: Sequentially forming a first reflective electrode material layer, a second reflective electrode material layer and a third reflective electrode material layer on the second undercut portion. The materials of the first reflective electrode material layer and the third reflective electrode material layer are indium tin oxide, and the material of the second reflective electrode material layer is silver.

13. The manufacturing method according to any one of claims 6 - 12, characterized in that, The reflective electrode is an anode.

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