A method for preparing a silicon-based OLED microcavity anode structure

Abstract

The application discloses a preparation method of a silicon-based OLED microcavity anode structure and belongs to the technical field of silicon-based OLED microcavity devices. The preparation method comprises the following steps: performing a yellow light process on a substrate to reserve photoresist between two adjacent sub-pixels on the substrate; after a metal reflection layer is deposited, a plurality of conductive film layers are deposited, and a yellow light process comprising negative photoresist coating is performed between adjacent two conductive film layers to reserve negative photoresist above a sub-pixel; and the microcavity anode structure is obtained after the photoresist is removed. The application has the beneficial effects that the process flow is reduced, the preparation efficiency is improved, the number of dry etching equipment and chemical vapor deposition equipment is reduced, the preparation cost is reduced, and the product yield and performance can be improved.

Description

Technical Field

[0001] This invention relates to the field of silicon-based OLED microcavity device technology, and in particular to a method for fabricating a silicon-based OLED microcavity anode structure. Background Technology

[0002] The current market demand for silicon-based Micro OLED displays is accelerating the improvement and optimization of their fabrication processes. Currently, due to the low yield of silicon-based Micro OLED devices, a simple single-layer anode structure is commonly chosen to avoid significant yield losses. While this structure is simple to manufacture, the uniform thickness of the anode sub-pixels makes effective matching with subsequent color filter layers impossible, resulting in impure light color and low light extraction efficiency. To achieve purer light extraction and higher efficiency, the BGR (Body Gland) of the device needs to have different cavity lengths. Since OLEDs are all of uniform thickness, different cavity lengths require different anode thicknesses in the BGR sub-pixels, thus creating a microcavity device.

[0003] Traditional fabrication of anodes with microcavity structures uses the Hard Mask process, which requires multiple physical deposition coatings, chemical deposition coatings, photolithography, dry etching, and wet stripping processes. This process involves many steps, places high demands on production equipment, and results in wasted production capacity and yield losses.

[0004] For example, patent CN113380967A discloses a method for fabricating a multilayer anode for a high-power microcavity device, including the following steps: S1. Forming a metal reflective layer and a B-anode; S2. B-HM preparation; during B-HM preparation, a PECVD film deposition process is performed on the wafer that has completed the B-anode process, selecting SiO or SiN film layers with a film thickness of 3000 Å to 4000 Å; S3. G-anode preparation; S4. G-HM preparation; S5. R-anode preparation; S6. HM removal, completing the multilayer anode fabrication. This fabrication method completes the multilayer anode fabrication through a four-mask process, including physical deposition, chemical deposition, photolithography, photolithography, and wet stripping. It has high requirements for equipment and processes, is complex, and multiple etching processes increase the risk of damage to the bottom film layer, affecting device performance. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for fabricating a silicon-based OLED microcavity anode structure. This method eliminates the need for a hard mask as a barrier layer and requires only physical deposition coating, photolithography, and wet stripping to obtain the anode of the microcavity structure. This reduces the number of process steps, improves fabrication efficiency, reduces the number of dry etching and chemical vapor deposition equipment, lowers fabrication costs, and increases product yield and performance.

[0006] To achieve the above objectives, the technical solution adopted by the present invention to solve its technical problem is: a method for preparing the silicon-based OLED microcavity anode structure, comprising the following steps:

[0007] Step 1: Perform photolithography on the substrate, retaining the photoresist between two adjacent sub-pixels on the substrate;

[0008] Step 2: After depositing the metal reflective layer, deposit multiple conductive film layers. Between the deposition of two adjacent conductive film layers, a photolithography process including negative photoresist coating is performed to retain a negative photoresist above the sub-pixel.

[0009] Step 3: After removing the photoresist, the microcavity anode structure is obtained.

[0010] Prior to step 1, substrate preparation is performed, including fabricating CMOS driving circuits on a silicon wafer substrate to form a CMOS substrate.

[0011] The specific process steps of step 1 are as follows:

[0012] 1) Coat the entire substrate with photoresist layer I;

[0013] 2) After exposure, development and baking, retain the photoresist layer I with an undercut profile between two adjacent sub-pixels on the substrate.

[0014] The photoresist layer I coated on the substrate is made of negative or positive photoresist. After exposure, development and baking under low light dose, the photoresist layer I between two adjacent sub-pixels on the substrate is retained, so that the photoresist layer I has an undercut profile.

[0015] The metal reflective layer is deposited using a material with good conductivity and reflectivity, including Ti, Al, TiN, or Ag; the conductive film layer is deposited using a transparent conductive oxide film with high work function, including ITO or IZO.

[0016] In step 2, a metal reflective layer and a multilayer conductive film are deposited using physical vapor deposition. The conductive film includes a first conductive film, a second conductive film, and a third conductive film deposited sequentially.

[0017] The sub-pixel types on the substrate include a first sub-pixel, a second sub-pixel, and a third sub-pixel, wherein the first sub-pixel, the second sub-pixel, or the third sub-pixel is one of a blue sub-pixel, a green sub-pixel, and a red sub-pixel.

[0018] The specific process steps of step 2 are as follows:

[0019] 1) Deposit a metallic reflective layer and a first conductive film layer;

[0020] 2) A negative photoresist layer II is coated on the entire surface. After exposure, development and baking, the negative photoresist layer II above the first sub-pixel is retained.

[0021] 3) Deposit the second conductive film layer;

[0022] 4) A negative photoresist layer Ⅲ is coated on the entire surface. After exposure, development and baking, the negative photoresist layer Ⅲ above the second sub-pixel is retained.

[0023] 5) Deposit the third conductive film layer.

[0024] In step 2), before exposing the negative photoresist layer II above the first sub-pixel, a photomask is used to cover and protect the area outside the negative photoresist layer II above the first sub-pixel; in step 4), before exposing the negative photoresist layer III above the second sub-pixel, a photomask is used to cover and protect the area outside the negative photoresist layer III above the second sub-pixel.

[0025] The microcavity anode structure obtained in step 3 includes a substrate, on which a metal reflective layer and a first conductive film layer are sequentially deposited at a position opposite to the first sub-pixel, a metal reflective layer, a first conductive film layer and a second conductive film layer are sequentially deposited at a position opposite to the second sub-pixel, and a metal reflective layer, a first conductive film layer, a second conductive film layer and a third conductive film layer are sequentially deposited at a position opposite to the third sub-pixel.

[0026] The beneficial effects of this invention are:

[0027] This invention provides a method for fabricating a silicon-based OLED microcavity anode structure. It eliminates the need for a hard mask as a barrier layer, employs a lift-off process, and utilizes a photolithography process including negative photoresist coating. Only physical deposition, photolithography, and wet stripping are required to obtain the anode of the microcavity structure, eliminating the need for chemical vapor deposition and dry etching processes. This reduces the number of steps, improves fabrication efficiency, decreases the number of dry etching and chemical vapor deposition equipment, lowers fabrication costs, and avoids the risk of damage to the bottom film layer due to repeated etching, thereby increasing product yield and performance. Attached Figure Description

[0028] The following is a brief explanation of the contents of each of the accompanying drawings and the markings in the drawings:

[0029] Figure 1 This is a schematic diagram of the structure of the first embodiment of the present invention, in which a photoresist layer I is coated on the entire surface of the substrate;

[0030] Figure 2 This is a schematic diagram of the structure of photoresist layer I exposed under low light dose in Embodiment 1 of the present invention;

[0031] Figure 3 To Figure 2 A schematic diagram of the obtained structure after development and baking;

[0032] Figure 4 This is a schematic diagram of the structure of the deposited metal reflective layer and the first conductive film layer of the present invention;

[0033] Figure 5 This is a schematic diagram of the structure of the present invention, in which a negative photoresist layer II is coated on the entire surface and exposed above the first sub-pixel;

[0034] Figure 6 To Figure 5 A schematic diagram of the structure obtained in the process after development and baking;

[0035] Figure 7 This is a schematic diagram of the structure of the second conductive film layer deposited in this invention;

[0036] Figure 8 This is a schematic diagram of the structure of the present invention, in which a negative photoresist layer Ⅲ is coated on the entire surface and the negative photoresist layer Ⅲ above the second sub-pixel is exposed.

[0037] Figure 9 To Figure 8 A schematic diagram of the structure obtained in the process after development and baking;

[0038] Figure 10 This is a schematic diagram of the structure of the third conductive film layer deposited in this invention;

[0039] Figure 11 This is a schematic diagram of the microcavity anode structure obtained after removing the negative photoresist according to the present invention;

[0040] The labels in the above figures are as follows: 1. Substrate, 2. Photoresist layer I, 3. Photomask, 4. Metal reflective layer, 5. First conductive film layer, 6. Negative photoresist layer II, 7. Second conductive film layer, 8. Negative photoresist layer III, 9. Third conductive film layer, 10. First sub-pixel, 11. Second sub-pixel, 12. Third sub-pixel. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below with reference to the accompanying drawings. The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0042] In the description of this invention, it should be noted that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0043] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0044] In existing technologies, the fabrication of anodes with microcavity structures using the Hard Mask process requires multiple physical deposition coatings, chemical deposition coatings, photolithography, dry etching, and wet stripping processes. This involves numerous steps, demands high-performance equipment, and results in wasted production capacity and yield losses. This invention addresses these problems by providing a method for fabricating silicon-based OLED microcavity anode structures. The following embodiments illustrate this method in detail.

[0045] Example 1

[0046] This invention provides a method for fabricating a silicon-based OLED microcavity anode structure, the fabrication process steps of which are as follows:

[0047] Step 1: Perform photolithography on substrate 1, retaining the photoresist between two adjacent sub-pixels on substrate 1;

[0048] Step 2: After depositing the metal reflective layer 4, deposit multiple conductive film layers. Between the deposition of two adjacent conductive film layers, a photolithography process including negative photoresist coating is performed to retain a negative photoresist above a sub-pixel.

[0049] Step 3: After removing the photoresist, the microcavity anode structure is obtained.

[0050] This invention does not use a hard mask as a barrier layer, but employs a lift-off process. It uses a photolithography process that includes negative photoresist coating, requiring only physical deposition, photolithography, and wet stripping to obtain the anode of the microcavity structure. This eliminates the need for chemical vapor deposition and dry etching processes, reducing the number of process steps, improving preparation efficiency, reducing the number of dry etching and chemical vapor deposition equipment, lowering preparation costs, and avoiding the risk of damage to the bottom film layer due to multiple etching processes, thus increasing product yield and performance.

[0051] The sub-pixels on the substrate 1 include a first sub-pixel 10, a second sub-pixel 11, and a third sub-pixel 12, wherein the first sub-pixel 10, the second sub-pixel 11, or the third sub-pixel 12 is one of a blue sub-pixel, a green sub-pixel, and a red sub-pixel. The multilayer conductive film includes a first conductive film layer 5, a second conductive film layer 7, and a third conductive film layer 9 deposited sequentially. The photoresist layer I2 is coated with a negative photoresist; the exposed portion of the negative photoresist is insoluble in the developer due to cross-linking and remains on the substrate 1, while the unexposed portion dissolves in the developer.

[0052] The specific preparation steps are as follows:

[0053] Step 1: Fabrication of substrate 1: Fabrication of CMOS driving circuits on a silicon wafer substrate to form CMOS substrate 1;

[0054] Step 2: As Figure 1 As shown, a negative photoresist is coated on the entire surface of substrate 1 to form photoresist layer I2;

[0055] Step 3: As Figure 2 As shown, a photomask 3 is used to cover the photoresist layer I2 above each sub-pixel on the protective substrate 1; exposure, development, and baking are performed under low light dose conditions. Under low light dose conditions, the photoresist layer I2 near the substrate 1 receives much less light than the surface of the photoresist layer I2, and the photoresist layer I2 near the substrate 1 maintains high solubility during the subsequent development process; as shown... Figure 3 As shown, after development and baking, the photoresist layer I2 between two adjacent sub-pixels on substrate 1 is retained, and the photoresist layer I2 has a clear undercut profile. The cross-sectional shape of the undercut profile is a trapezoidal structure with the upper base longer than the lower base.

[0056] Step 4: As Figure 4 As shown, a metal reflective layer 4 and a first conductive film layer 5 are deposited using physical vapor deposition. The metal reflective layer 4 is deposited using a material with good conductivity and reflectivity, such as Ti, Al, TiN, or Ag. The first conductive film layer 5 is deposited using a transparent conductive oxide thin film with a high work function, such as ITO or IZO.

[0057] Step 5: As Figure 5 As shown, a negative photoresist layer II6 is coated on the entire surface. A photomask 3 is used to cover and protect the area above the first sub-pixel 10 except for the negative photoresist layer II6, and the negative photoresist layer II6 above the first sub-pixel 10 is exposed.

[0058] Step 6: As Figure 6 As shown, after development and baking, the negative photoresist layer II6 above the first sub-pixel 10 is retained.

[0059] Step 7: As Figure 7 As shown, the second conductive film layer 7 is deposited by physical vapor deposition. The second conductive film layer 7 is deposited using a transparent conductive oxide thin film with a high work function. The materials used include ITO or IZO.

[0060] Step 8: As Figure 8 As shown, a negative photoresist layer Ⅲ8 is coated across the entire surface. A photomask 3 is used to cover and protect the area above the second sub-pixel 11 except for the area above the negative photoresist layer Ⅲ8, and then the negative photoresist layer Ⅲ8 above the second sub-pixel 11 is exposed. Figure 9 As shown, after development and baking, the negative photoresist layer Ⅲ8 above the second sub-pixel 11 is retained;

[0061] Step 9: As Figure 10 As shown, the third conductive film layer 9 is deposited by physical vapor deposition. The third conductive film layer 9 is a transparent conductive oxide thin film with a high work function, and the materials used include ITO or IZO.

[0062] Step 10: As Figure 11 As shown, after removing the retained photoresist layer I2, negative photoresist layer II6, and negative photoresist layer III8 using a resist remover, a microcavity anode structure is obtained. The microcavity anode structure includes a substrate 1. A metal reflective layer 4 and a first conductive film layer 5 are sequentially deposited on the substrate 1 at a position opposite to the first sub-pixel 10. A metal reflective layer 4, a first conductive film layer 5, and a second conductive film layer 7 are sequentially deposited on the substrate 1 at a position opposite to the second sub-pixel 11. A metal reflective layer 4, a first conductive film layer 5, a second conductive film layer 7, and a third conductive film layer 9 are sequentially deposited on the substrate 1 at a position opposite to the third sub-pixel 12.

[0063] Example 2

[0064] The difference from Example 1 is that the photoresist layer I2 is coated with positive photoresist. The exposed portion of the positive photoresist undergoes a photochemical reaction and dissolves in the developer, while the unexposed portion does not dissolve in the developer and remains on the substrate 1.

[0065] Therefore, this embodiment differs from the preparation method in Embodiment 1, which preserves the photoresist layer I2 between two adjacent sub-pixels on substrate 1, and the photoresist layer I2 exhibits a distinct undercut profile. The specific method is as follows:

[0066] 1) A positive photoresist is coated on the entire surface of substrate 1 to form photoresist layer I2;

[0067] 2) Use photomask 3 to cover the photoresist layer I2 on the substrate 1, except for the area above each sub-pixel; expose, develop, and bake the photoresist layer I2 above each sub-pixel under low light dose conditions. Under low light dose conditions, the photoresist layer I2 near the substrate 1 receives much less light than the surface of the photoresist layer I2, and maintains high solubility of the photoresist layer I2 near the substrate 1 during the subsequent development process; such as Figure 3 As shown, after development and baking, the photoresist layer I2 between two adjacent sub-pixels on substrate 1 is retained, and the photoresist layer I2 has a clear undercut profile. The cross-sectional shape of the undercut profile is a trapezoidal structure with the upper base longer than the lower base.

[0068] In summary, this invention does not use a hard mask as a barrier layer. It only requires physical deposition coating, photolithography, and wet stripping to obtain the anode with a microcavity structure. This reduces the number of process steps, improves the preparation efficiency, reduces the number of dry etching and chemical vapor deposition equipment, lowers the preparation cost, and can also increase product yield and performance.

[0069] The above description is merely an illustration of some principles of the present invention. This specification is not intended to limit the present invention to the specific structures and applicable scope shown. Therefore, all possible modifications and equivalents that may be used fall within the scope of the patent application of this invention.

Claims

1. A method for fabricating a silicon-based OLED microcavity anode structure, characterized in that, Includes the following steps: Step 1: Perform photolithography on the substrate, retaining the photoresist between two adjacent sub-pixels on the substrate; the specific process steps of Step 1 are: 1) Coat the entire surface of the substrate with photoresist layer I; 2) After exposure, development and baking, retain the photoresist layer I with an undercut profile between two adjacent sub-pixels on the substrate. Step 2: After depositing the metal reflective layer, deposit multiple conductive film layers. Between the deposition of adjacent conductive film layers, a photolithography process including negative photoresist coating is performed to retain negative photoresist above a sub-pixel. The conductive film layers include a first conductive film layer, a second conductive film layer, and a third conductive film layer deposited sequentially. The sub-pixel types on the substrate include a first sub-pixel, a second sub-pixel, and a third sub-pixel, wherein the first sub-pixel, the second sub-pixel, or the third sub-pixel is one of a blue sub-pixel, a green sub-pixel, and a red sub-pixel. The specific process steps of step 2 are as follows: 1) depositing a metal reflective layer and a first conductive film layer; 2) coating the entire surface with a negative photoresist layer II, and retaining the negative photoresist layer II above the first sub-pixel after exposure, development and baking; 3) depositing a second conductive film layer; 4) coating the entire surface with a negative photoresist layer III, and retaining the negative photoresist layer III above the second sub-pixel after exposure, development and baking. 5) Deposit the third conductive film layer; Step 3: After removing the photoresist, the microcavity anode structure is obtained.

2. The method for fabricating a silicon-based OLED microcavity anode structure according to claim 1, characterized in that: Prior to step 1, substrate preparation is performed, including fabricating CMOS driving circuits on a silicon wafer substrate to form a CMOS substrate.

3. The method for fabricating a silicon-based OLED microcavity anode structure according to claim 1, characterized in that: The photoresist layer I coated on the substrate is made of negative or positive photoresist. After exposure, development and baking under low light dose, the photoresist layer I between two adjacent sub-pixels on the substrate is retained, so that the photoresist layer I has an undercut profile.

4. The method for fabricating a silicon-based OLED microcavity anode structure according to claim 1, characterized in that: The metal reflective layer is deposited using a material with good conductivity and reflectivity, including Ti, Al, TiN, or Ag; the conductive film layer is deposited using a transparent conductive oxide film with high work function, including ITO or IZO.

5. The method for fabricating a silicon-based OLED microcavity anode structure according to claim 1, characterized in that: In step 2, a metal reflective layer and a multilayer conductive film are deposited using physical vapor deposition.

6. The method for fabricating a silicon-based OLED microcavity anode structure according to claim 1, characterized in that: In step 2), before exposing the negative photoresist layer II above the first sub-pixel, a photomask is used to cover and protect the area outside the negative photoresist layer II above the first sub-pixel; in step 4), before exposing the negative photoresist layer III above the second sub-pixel, a photomask is used to cover and protect the area outside the negative photoresist layer III above the second sub-pixel.

7. The method for fabricating a silicon-based OLED microcavity anode structure according to claim 1, characterized in that: The microcavity anode structure obtained in step 3 includes a substrate, on which a metal reflective layer and a first conductive film layer are sequentially deposited at a position opposite to the first sub-pixel, a metal reflective layer, a first conductive film layer and a second conductive film layer are sequentially deposited at a position opposite to the second sub-pixel, and a metal reflective layer, a first conductive film layer, a second conductive film layer and a third conductive film layer are sequentially deposited at a position opposite to the third sub-pixel.

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