Mask manufacturing method and mask

Abstract

The present invention relates to the technical field of silicon-based OLEDs. Disclosed are a mask manufacturing method and a mask. The mask manufacturing method comprises: providing a silicon-based substrate; forming a metal seed layer on the surface of the silicon-based substrate; forming a first photoresist layer on the surface of the metal seed layer; forming, on the surface of the first photoresist layer, a plurality of first windows exposing part of the metal seed layer; forming, on the surface of the metal seed layer facing the first windows, a mask layer filling the first windows by an electroforming process; and removing the first photoresist layer, the silicon-based substrate, and the metal seed layer to obtain a mask. In the present invention, the mask is manufactured by combining a photolithography process and the electroforming process, wherein the opening width of the mask depends on the precisions of exposure, development and photoresist removal during the photolithography process. Compared with the existing calendering and etching processes, the manufacturing method provided by the present application can reduce the minimum opening dimension of the mask, such that the mask can be applied to manufacturing of silicon-based OLED display devices with higher PPI.

Description

Mask fabrication method and mask

[0001] This application claims priority to Chinese Patent Application No. 202411487151.4, filed on October 23, 2024, entitled “Method for Making a Mask and Mask”, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This invention relates to the field of silicon-based OLED technology, and in particular to a method for fabricating a photomask and the photomask itself. Background Technology

[0003] There are two main technological routes for achieving full-color display in silicon-based OLEDs:

[0004] 1. WOLED+CF silicon-based OLED, which uses WOLED (White OLED, white organic light-emitting diode) as the backlight and achieves full-color display through CF (Color Filter);

[0005] 2. RGB silicon-based OLED, which achieves full-color display by directly depositing organic light-emitting materials onto specific areas of a silicon substrate to form RGB sub-pixels.

[0006] Compared to WOLED+CF silicon-based OLED, the RGB silicon-based OLED method mentioned above has higher luminous efficiency and lower energy consumption because it directly displays the three primary colors. Therefore, it is being increasingly used in the field of silicon-based OLED.

[0007] In the process of RGB silicon-based OLEDs, dense and tiny RGB OLED sub-pixels need to be deposited on a silicon substrate using a mask. The minimum aperture size on the mask corresponds to the minimum size of the RGB OLED sub-pixel. Therefore, to achieve a higher PPI (Pixels Per Inch) in silicon-based OLED displays, the aperture size on the mask needs to be reduced.

[0008] Currently, the primary material used for subpixel masks is Invar, mainly because Invar is a magnetic material and has a low coefficient of thermal expansion. When depositing organic light-emitting materials onto the backplate in the evaporation chamber, magnetic plates can be used to hold the mask in place, reducing sagging due to gravity and minimizing display issues caused by uneven deposition of the organic light-emitting materials. Furthermore, the low coefficient of thermal expansion reduces the positional deviation of the RGB subpixels during evaporation.

[0009] In traditional mask manufacturing processes, Invar masks are produced using calendering and etching methods. Calendering thins the Invar mask, reducing its thickness; then etching creates openings at the corresponding RGB subpixel positions to obtain the desired mask shape. However, due to limitations in Invar material and calendering processes, the thickness of Invar masks can only be reduced to a minimum of 15μm. Furthermore, the size of the etched openings is directly proportional to the mask's thickness. Limited by etching technology capabilities, the minimum opening width for existing masks can only be 15μm.

[0010] In summary, the thickness and aperture size of Invar material masks under existing manufacturing processes are relatively large, making it difficult for existing masks to meet the technical requirements of silicon-based OLEDs for full-color display at high PPI. Summary of the Invention

[0011] The main objective of this invention is to propose a mask fabrication method and a mask, aiming to solve the problem that the existing manufacturing process technology has a large thickness and large opening size of the Invar Mask, which makes it impossible to meet the technical requirements of silicon-based OLED for full-color display at high PPI.

[0012] To achieve the above objectives, the present invention proposes a photomask fabrication method, the photomask fabrication method comprising:

[0013] Provide silicon-based substrates;

[0014] A metal seed layer is formed on the surface of the silicon substrate;

[0015] A first photoresist layer is formed on the surface of the metal seed layer;

[0016] A plurality of first windows are formed on the surface of the first photoresist layer to expose portions of the metal seed layer;

[0017] A mask layer filling each of the first windows is formed on the surface of the metal seed layer facing the first window using an electroforming process;

[0018] Remove the first photoresist layer, the silicon substrate, and the metal seed layer to obtain a photomask.

[0019] In one embodiment of the present invention, the step of forming a mask layer filling each of the first windows on the surface of the metal seed layer facing the first window by an electroforming process includes:

[0020] The metal seed layer is electrically connected to the electroforming cathode, and the Invar alloy material is electrically connected to the electroforming anode;

[0021] The silicon substrate on which the metal seed layer is formed is placed in the electroforming solution;

[0022] The electroformed cathode and the electroformed anode are energized for a preset time to obtain the mask layer.

[0023] In one embodiment of the present invention, the step of electrically connecting the metal seed layer to the electroforming cathode includes:

[0024] Provide conductive carriers;

[0025] The silicon substrate is placed into the conductive carrier, so that the metal seed layer is in contact with the conductive carrier;

[0026] The conductive carrier is electrically connected to the electroformed cathode.

[0027] In one embodiment of the present invention, the step of forming a plurality of first windows on the surface of the first photoresist layer to expose a portion of the metal seed layer includes:

[0028] Provide photomasks;

[0029] Multiple light-transmitting openings are formed on the surface of the photomask;

[0030] The photomask is used to expose and develop the surface of the first photoresist layer, so that the first photoresist layer forms a first window between every two adjacent light-transmitting holes.

[0031] In one embodiment of the present invention, the step of removing the first photoresist layer, the silicon substrate, and the metal seed layer includes:

[0032] Remove the first photoresist layer to form multiple openings on the surface of the mask layer;

[0033] A second photoresist layer is formed on the side of the silicon substrate opposite to the metal seed layer;

[0034] The second photoresist layer is exposed and developed;

[0035] The first etched area of ​​the silicon substrate covering each of the openings of the mask layer and the second etched area of ​​the metal seed layer covering each of the openings of the mask layer are sequentially etched to form a support frame composed of the silicon substrate and the metal seed layer.

[0036] In one embodiment of the present invention, after the step of removing the first photoresist layer to form a plurality of openings on the surface of the mask layer and before the step of forming a second photoresist layer on the side of the silicon substrate opposite to the metal seed layer, the following is further included:

[0037] A third photoresist layer is formed on the surface of the mask layer and the metal seed layer, the third photoresist layer covering the surface of the mask layer and filling each of the openings.

[0038] In one embodiment of the present invention, after the step of etching the second etched region of the metal seed layer covering each of the openings of the mask layer, the method further includes:

[0039] Remove the second and third photoresist layers.

[0040] The present invention also proposes a mask, the mask comprising a support frame and a mask layer; the mask layer is disposed on the support frame, and the surface of the mask layer has a plurality of openings, the openings being used to pass through the deposition material during OLED pixel layer deposition to form the OLED pixel layer.

[0041] In one embodiment of the present invention, the cross-sectional shape of the opening is rectangular, and the width of the opening is L, where 2um ≤ L ≤ 15um.

[0042] In one embodiment of the present invention, the support frame is disposed along the edge of the mask layer and located on one side of the mask layer; the support frame includes a metal seed layer and a silicon substrate stacked sequentially in a direction perpendicular to the mask layer, wherein the metal seed layer is located on the surface of the mask layer.

[0043] In one embodiment of the present invention, the metal seed layer includes a nickel layer and an aluminum layer stacked sequentially in a direction away from the mask layer, wherein the nickel layer is located on the surface of the silicon substrate.

[0044] The photomask fabrication method proposed in this invention includes forming a metal seed layer on the surface of a provided silicon substrate using processes such as deposition or coating; then coating the surface of the metal seed layer with photoresist to form a first photoresist layer; and then exposing and developing the first photoresist layer to form multiple first windows, exposing the areas of the metal seed layer corresponding to the first windows within the first windows. Subsequently, Invar alloy material is electroformed onto the surface of the metal seed layer exposed at the first windows using an electroforming process, i.e., the Invar alloy material fills the first windows to form the photomask layer. Since the first photoresist layer is a non-conductive material, Invar alloy material is not deposited on its surface during electroforming. Therefore, after removing the first photoresist layer using an etching process, the areas where the first photoresist layer was originally formed correspond to the openings of the photomask. This application fabricates a photomask by combining photolithography and electroforming processes. The width of the opening in the photomask depends on the precision of exposure, development, and resist removal during the photolithography process. Compared to existing calendering and etching processes, the fabrication method proposed in this application can reduce the minimum opening size of the photomask, enabling the photomask to be used in the manufacture of silicon-based OLED display devices with higher PPI. Attached Figure Description

[0045] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0046] Figure 1 is a flowchart of the mask fabrication method provided by the present invention in one embodiment;

[0047] Figure 2 is a flowchart of the steps of forming a mask layer filling each first window on the surface of the metal seed layer facing the first window using an electroforming process, as shown in Figure 1.

[0048] Figure 3 is a flowchart of the steps for electrically connecting the electroformed cathode to the metal seed layer in Figure 2.

[0049] Figure 4 is a flowchart of the steps for forming multiple first windows on the surface of the first photoresist layer that expose a portion of the metal seed layer as shown in Figure 1.

[0050] Figure 5 is a flowchart of the steps in Figure 1 for removing the first photoresist layer, silicon substrate and metal seed layer;

[0051] Figure 6 is a flowchart of the steps before forming the second photoresist layer on the side of the silicon substrate opposite to the metal seed layer in Figure 5;

[0052] Figure 7 is a flowchart of the steps after the second etching area of ​​the mask layer is covered by the etching metal seed layer in Figure 5.

[0053] Figure 8 is a structural schematic diagram of the mask fabrication method provided by the present invention in the first embodiment;

[0054] Figure 9 is a schematic diagram of the mask fabrication method provided by the present invention in the second embodiment;

[0055] Figure 10 is a structural schematic diagram of the mask fabrication method provided by the present invention in the third embodiment;

[0056] Figure 11 is a schematic diagram of the mask fabrication method provided by the present invention in the fourth embodiment;

[0057] Figure 12 is a structural schematic diagram of the mask fabrication method provided by the present invention in the fifth embodiment;

[0058] Figure 13 is a schematic diagram of the mask fabrication method provided by the present invention in the sixth embodiment;

[0059] Figure 14 is a structural schematic diagram of the mask fabrication method provided by the present invention in the seventh embodiment;

[0060] Figure 15 is a structural schematic diagram of the mask fabrication method provided by the present invention in the eighth embodiment;

[0061] Figure 16 is a structural schematic diagram of the mask fabrication method provided by the present invention in the ninth embodiment;

[0062] Figure 17 is a structural schematic diagram of the mask fabrication method provided by the present invention in the tenth embodiment;

[0063] Figure 18 is a structural schematic diagram of the mask fabrication method provided by the present invention in the eleventh embodiment;

[0064] Figure 19 is a structural schematic diagram of the mask fabrication method provided by the present invention in the twelfth embodiment;

[0065] Figure 20 is a schematic diagram of the structure of the mask provided by the present invention.

[0066] Explanation of reference numerals: 10, silicon substrate; 11, first etched area; 20, metal seed layer; 21, second etched area; 30, first photoresist layer; 31, first window; 40, mask layer; 41, opening; 50, second photoresist layer; 60, third photoresist layer; 70, photomask; 71, light-transmitting aperture; 80, conductive carrier; 90, support frame.

[0067] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0068] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0069] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indications will also change accordingly.

[0070] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or" or "and / or" throughout the text includes three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0071] This invention proposes a method for fabricating a photomask.

[0072] Referring to Figures 1, 8 to 15, and 20, in one embodiment of the present invention, the method for fabricating a photomask includes:

[0073] Provide a silicon substrate 10;

[0074] S100: A metal seed layer 20 is formed on the surface of a silicon substrate 10;

[0075] S200: A first photoresist layer 30 is formed on the surface of the metal seed layer 20;

[0076] S300: A plurality of first windows 31 are formed on the surface of the first photoresist layer 30 to expose a portion of the metal seed layer 20;

[0077] S400: A mask layer 40 filling each first window 31 is formed on the surface of the metal seed layer 20 facing the first window 31 by an electroforming process;

[0078] S500: Remove the first photoresist layer 30, the silicon substrate 10, and the metal seed layer 20 to obtain a photomask.

[0079] In this embodiment, the silicon substrate 10 can be 4 inches, 6 inches, or 12 inches in size. The silicon substrate 10 is thinned by grinding to meet the thickness requirements. The metal seed layer 20 can be composed of one or more metal composite plating materials such as nickel (Ni), aluminum (Al), and titanium (Ti). The metal seed layer 20 can be formed on the surface of the silicon substrate 10 by deposition or electroplating. Forming the metal seed layer 20 on the substrate is a key step in the electroforming mask fabrication process, and its main purposes and functions include:

[0080] 1. Electrical Conductivity: The electroforming process requires current to pass through the electroforming cathode and anode, and the substrate material (such as silicon) is usually a semiconductor. By depositing a metal seed layer 20 on the silicon substrate 10, the metal seed layer 20 can serve as the electroforming cathode, allowing current to flow during the electroforming process, thereby achieving the reduction and deposition of metal ions of the mask material on the surface of the metal seed layer 20.

[0081] 2. Providing nucleation sites: The metal seed layer 20 provides nucleation sites for the transformation of mask material metal particles in the electroforming solution into the solid mask layer 40 during the electroforming process. That is, after the metal cations are reduced in the electroforming solution, they are first deposited on the metal seed layer 20. These initially deposited metals form the adhesion basis for subsequent deposition, promoting the uniform growth of the electroformed layer.

[0082] 3. Improved Adhesion: The metal seed layer 20 can increase the adhesion between the mask layer 40 and the silicon substrate 10. Compared to silicon, the lattice structure of the composite coating material of the metal seed layer 20 is closer to that of the mask layer 40 material (Invar alloy) and the silicon substrate 10. Therefore, the metal seed layer 20 has good bonding force with the substrate and the electroforming material, which helps to improve the adhesion between the mask layer 40 and the substrate and prevent the mask layer 40 from peeling or falling off from the silicon substrate 10 during subsequent processing.

[0083] Photoresist is applied to the surface of the metal seed layer 20 to form a first photoresist layer 30. Multiple first windows 31 are then formed on the first photoresist layer 30 using a photolithography process. Thus, the metal seed layer 20 is partially obscured by the first photoresist layer 30, while partially exposed through the first windows 31. Since the first photoresist layer 30 is an organic material with insulating properties, a mask material (Invar alloy) is deposited and filled onto the surface of the metal seed layer 20 at the first windows 31 during electroforming. After electroforming is complete, the first photoresist layer 30 between the first windows 31 is etched away, forming the openings 41 of the mask layer 40.

[0084] As described above, the mask fabrication method proposed in this application does not directly etch the mask layer 40. Instead, it uses a combination of photolithography and electroforming. First, the first photoresist layer 30 is exposed and developed, then electroformed, and finally etched to form the mask. Therefore, the size of the opening 41 on the mask surface is related to the precision of the photolithography process. Compared to existing mask fabrication methods using calendering and etching, the method proposed in this application can reduce the minimum opening size of the mask, enabling the mask to be used in the manufacture of silicon-based OLED display devices with higher PPI.

[0085] As shown in Figure 2, in one embodiment of the present invention, the step of forming a mask layer 40 filling each first window 31 on the surface of the metal seed layer 20 facing the first window 31 by an electroforming process includes:

[0086] S410: Electrically connect the metal seed layer 20 to the electroforming cathode and electrically connect the Invar alloy material to the electroforming anode;

[0087] S420: The silicon substrate 10 with the metal seed layer 20 formed thereon is placed in the electroforming solution;

[0088] S430: Electrify the electroformed cathode and electroformed anode for a preset time to obtain the mask layer 40.

[0089] In this embodiment, the mask material is made of electroformed metal, specifically Invar alloy. The metal seed layer 20 and the mask material are connected to the cathode and anode of the power supply respectively via wires. The wires can be electrically connected to the metal seed layer 20 using conductive adhesives or welding. Alternatively, the wires can be connected to a clamping device, which is then clamped onto the silicon substrate 10 on which the seed layer is deposited, to achieve electrical connection between the power supply cathode and the metal seed layer 20. Alternatively, the silicon substrate 10 on which the metal seed layer 20 is deposited can be placed in a conductive carrier 80, and the wires can be electrically connected to the conductive carrier 80 to achieve electrical connection between the power supply cathode and the metal seed layer 20.

[0090] The electroforming cathode (i.e., the silicon substrate 10 with the metal seed layer 20) and the electroforming anode (i.e., the mask material) are both placed in an electroforming tank filled with electroforming solution. The electroforming anode and cathode are electrically connected through the electroforming solution containing metal ions. When the power is turned on, the metal atoms of the electroforming anode lose electrons and become metal cations that enter the electroforming solution. The electroforming cathode attracts these metal ions, causing them to gain electrons and be reduced back to metal atoms, which are then deposited on the surface of the electroforming cathode to form an electroforming layer (i.e., the portion of the metal seed layer 20 exposed at the first window 31). By controlling the current density and electroforming time during the electroforming process, a mask layer 40 of the desired thickness can be obtained.

[0091] Furthermore, since metal ions of the mask material will deposit and fill each first window 31 during the electroforming process, when the thickness of the mask layer 40 to be electroformed is greater than the depth of the first window 31, the mask layer 40 that protrudes above the surface of the first photoresist layer 30 will exhibit an arch shape during electroforming, resulting in an uneven surface of the final mask and the inability of the opening 41 of the mask to meet the forming accuracy requirements.

[0092] Therefore, when coating the first photoresist layer 30 on the surface of the metal seed layer 20, the thickness of the coated first photoresist layer 30 is controlled to be greater than or equal to the thickness of the mask layer 40 to be electroformed, that is, the depth of the first window 31 is greater than or equal to the thickness of the mask layer 40 to be electroformed, so that after electroforming, the height of the mask layer 40 is flush with or lower than the first photoresist layer 30, so as to ensure that the processing accuracy of the mask meets the requirements.

[0093] Referring to Figures 3 and 13, in one embodiment of the present invention, the step of electrically connecting the metal seed layer 20 to the electroforming cathode includes:

[0094] Provide conductive carrier 80;

[0095] S411: Place the silicon substrate 10 into the conductive carrier 80, so that the metal seed layer 20 is in contact with the conductive carrier 80;

[0096] S412: Electrically connect the conductive carrier 80 to the electroformed cathode.

[0097] In this embodiment, the conductive carrier 80 is made of copper (Cu). Additionally, a layer of nickel or chromium is electroplated on the outer surface of the conductive carrier 80 to further improve its conductivity and corrosion resistance. The size of the conductive carrier 80 matches the size of the silicon substrate 10. The silicon substrate 10 is placed inside the conductive carrier 80, with the peripheral portion of the metal seed layer 20 in contact with the conductive carrier 80, thus electrically connecting the metal seed layer 20 to the conductive carrier 80. The conductive carrier 80 is electrically connected to the cathode of the electroforming power supply, thereby achieving electrical connection between the metal seed layer 20 and the power supply cathode. Compared to directly connecting the metal seed layer 20 to the power supply cathode, in this embodiment, the metal seed layer 20 is connected to the power supply cathode via the conductive carrier 80. The wires of the power supply cathode can be connected to the conductive carrier 80 by soldering or by clamping with a clamping device. These connection methods do not damage the silicon substrate 10 or the metal seed layer 20, thereby improving the mask production yield.

[0098] Referring to Figures 4, 11, and 12, in one embodiment of the present invention, the step of forming a plurality of first windows 31 on the surface of the first photoresist layer 30 that expose a portion of the metal seed layer 20 includes:

[0099] Provide photomask 70;

[0100] S310: Multiple light-transmitting openings 71 are formed on the surface of the photomask 70;

[0101] S320: Expose and develop the surface of the first photoresist layer 30 using the photomask 70, so that the first photoresist layer 30 forms a first window 31 between every two adjacent light-transmitting holes 71.

[0102] In this embodiment, the photomask 70 is used to transfer a pre-formed pattern onto the first photoresist layer 30. Specifically, the photoresist in the first photoresist layer 30 is a negative photoresist. During the exposure reaction, the chemical structure of the exposed portion of the first photoresist layer 30 changes, making the photoresist in the exposed area insoluble in the developer. During the development process, the unexposed photoresist portion is dissolved by the developer, while the exposed photoresist portion is retained, thereby transferring the pattern of the light-transmitting aperture 71 of the photomask 70 to the first photoresist layer 30. Therefore, by controlling the position, size, shape, and spacing of the light-transmitting aperture 71 of the photomask 70, the position, size, shape, and spacing of the first window 31 can be controlled, thereby controlling the position, size, shape, and spacing of the mask opening 41. For example, in this embodiment, the light-transmitting aperture 71 of the photomask 70 corresponds to the opening 41 on the final mask. Therefore, by controlling the width of the light-transmitting aperture 71 of the photomask 70 to 2um to 15um, an opening 41 with a width of 2um to 15um can be obtained on the mask.

[0103] Referring to Figures 5, 16 to 19, in one embodiment of the present invention, the step of removing the first photoresist layer 30, the silicon substrate 10, and the metal seed layer 20 includes:

[0104] S510: Remove the first photoresist layer 30 to form a plurality of openings 41 on the surface of the mask layer 40;

[0105] S520: A second photoresist layer 50 is formed on the side of the silicon substrate 10 opposite to the metal seed layer 20;

[0106] S530: Expose and develop the second photoresist layer 50;

[0107] S540: Sequentially etching the first etching region 11 of the silicon substrate 10 covering each opening 41 of the mask layer 40, and the second etching region 21 of the metal seed layer 20 covering each opening 41 of the mask layer 40, to form a support frame 90 composed of the silicon substrate 10 and the metal seed layer 20.

[0108] In this embodiment, when depositing organic light-emitting materials using the mask fabricated in this application, the mask layer 40 and the evaporation platform are spaced apart. Therefore, a support frame 90 needs to be provided on one side of the mask layer 40 to elevate the mask layer 40 to a certain height. In this application, during mask fabrication, the metal seed layer 20 and the silicon substrate 10 on one side of the mask layer 40 are etched to form the support frame 90. Compared to a solution where the support frame 90 is soldered onto the mask layer 40, this embodiment simplifies the process steps and also improves the processing accuracy of the support frame 90.

[0109] Specifically, in this embodiment, photoresist is first applied to the side of the silicon substrate 10 opposite to the metal seed layer 20 by spin-spraying to form a second photoresist layer 50. Then, the second photoresist layer 50 is exposed and developed. After development, the first etched area 11 of the silicon substrate 10 is exposed, while other areas are masked by the second photoresist layer 50. Then, different chemical solvents or etching gases are used sequentially to remove the first etched area 11 of the silicon substrate 10 and the second etched area 21 of the metal seed layer 20, ultimately exposing the openings 41 of the mask layer 40. The unetched silicon substrate 10 and metal seed layer 20, masked by the second photoresist layer 50, together form the support frame 90. Depending on the actual requirements for organic material deposition, the support frame 90 is etched into different shapes and sizes.

[0110] Referring to Figures 6 and 16, in one embodiment of the present invention, after the step of removing the first photoresist layer 30 to form a plurality of openings 41 on the surface of the mask layer 40 and before the step of forming the second photoresist layer 50 on the side of the silicon substrate 10 opposite to the metal seed layer 20, the method further includes:

[0111] S511: A third photoresist layer 60 is formed on the surface of the mask layer 40 and the metal seed layer 20. The third photoresist layer 60 covers the surface of the mask layer 40 and fills each opening 41.

[0112] When performing processes such as photolithography, electroforming, and etching, the photolithography area, electroforming area, and etching area usually need to face upwards. That is, when the mask layer 40 is completed, before etching the silicon substrate 10 and the metal seed layer 20, the wafer needs to be flipped so that the mask layer 40 faces downwards and the silicon substrate 10 faces upwards.

[0113] Therefore, in this embodiment, before applying the second photoresist layer 50, a third photoresist layer 60 is first applied to the surface of the mask layer 40. The addition of the third photoresist layer 60 can protect the mask layer 40 from damage during subsequent development, etching and flipping processes.

[0114] Referring to Figures 7, 19, and 20, in one embodiment of the present invention, after the step of etching the second etched region 21 of each opening 41 of the mask layer 40 by the etched metal seed layer 20, the method further includes:

[0115] S550: Remove the second photoresist layer 50 and the third photoresist layer 60.

[0116] In this embodiment, the second photoresist layer 50 and the third photoresist layer 60 can be removed by a developer or by plasma etching. After removing the second photoresist layer 50 and the third photoresist layer 60, the mask layer 40 and the support frame 90 are fully exposed, forming a complete mask structure.

[0117] The present invention also proposes a photomask, the fabrication method of which refers to the above embodiments. As shown in FIG20, the photomask includes a support frame 90 and a mask layer 40. The mask layer 40 is disposed on the support frame 90, and a plurality of openings 41 are formed on the surface of the mask layer 40. The openings 41 are used to allow the deposition material to pass through during the deposition of the OLED pixel layer to form the OLED pixel layer.

[0118] In this embodiment, the mask is used to deposit organic light-emitting materials onto a backplane when fabricating high-resolution OLED display devices. The mask layer 40 is made of Invar alloy, which has a low coefficient of thermal expansion to accommodate high-temperature deposition processes. Simultaneously, the mask layer 40 is magnetic. During organic light-emitting material deposition, a magnetic chuck can be placed on the side of the backplane away from the mask, allowing the mask to adhere to the backplane surface under the magnetic force of the chuck. This prevents the central area of ​​the mask from sagging due to gravity, thus solving the problem of uneven deposition during organic light-emitting layer deposition.

[0119] The support frame 90 provides good mechanical support for the mask layer 40, and the support frame 90 avoids the opening 41 of the mask layer 40, so that the mask layer 40 and the evaporation platform are spaced apart during the deposition of organic light-emitting materials. The thickness of the support frame 90 can be set according to the spacing requirements between the mask layer 40 and the evaporation platform during the deposition of organic light-emitting materials, and is not further limited here.

[0120] In one embodiment of the present invention, the cross-sectional shape of the opening 41 is rectangular, and the width of the opening 41 is L, where 2µm ≤ L ≤ 15µm. By controlling the size, shape, and spacing of the first window 31 opened in the first photoresist layer 30 during mask fabrication, a mask with the desired size and shape of the opening 41 is obtained. During organic light-emitting material deposition, the pattern of the opening 41 is transferred to the OLED pixel layer through the mask to obtain RGB pixel units with the same size as the opening 41, thereby meeting the precision requirements of high PPI display devices.

[0121] Referring to Figure 20, in one embodiment of the present invention, a support frame 90 is disposed along the edge of the mask layer 40 and on one side of the mask layer 40; the support frame 90 includes a metal seed layer 20 and a silicon substrate 10 stacked sequentially in a direction perpendicular to the mask layer 40, wherein the metal seed layer 20 is located on the surface of the mask layer 40.

[0122] In this embodiment, the support frame 90 can be configured as a ring to provide a larger contact area with the mask layer 40 and to ensure more uniform support at different locations on the mask layer 40. The outer peripheral surface of the support frame 90 is flush with the outer peripheral surface of the mask layer 40. The support frame 90 includes a metal seed layer 20 and a silicon substrate 10 stacked sequentially along a direction perpendicular to the mask layer 40. The metal seed layer 20 can be one or more combinations of metal materials such as nickel, aluminum, copper, and titanium. The metal seed layer 20 improves the adhesion between the mask layer 40 and the silicon substrate 10, ensuring that the mask has good mechanical and thermal stability.

[0123] Referring to Figure 9, in one embodiment of the present invention, the metal seed layer 20 includes a nickel layer and an aluminum layer stacked sequentially in a direction away from the mask layer 40, with the nickel layer located on the surface of the silicon substrate 10.

[0124] In this embodiment, the nickel layer has a better lattice structure than the silicon substrate 10, resulting in better bonding strength. Similarly, the aluminum layer has a better lattice structure than the electroformed mask layer 40, also resulting in better bonding strength. Therefore, this dual-layer structure design further enhances the bonding strength between the silicon substrate 10 and the mask layer 40. In other embodiments, nickel and aluminum can be inter-doped to form a metal seed layer 20.

[0125] The above description is merely an exemplary embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention specification and drawings under the technical concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for fabricating a photomask, characterized in that, The method for fabricating the photomask includes: Provide silicon-based substrates; A metal seed layer is formed on the surface of the silicon substrate; A first photoresist layer is formed on the surface of the metal seed layer; A plurality of first windows are formed on the surface of the first photoresist layer to expose portions of the metal seed layer; A mask layer filling each of the first windows is formed on the surface of the metal seed layer facing the first window using an electroforming process; Remove the first photoresist layer, the silicon substrate, and the metal seed layer to obtain a photomask.

2. The method for fabricating a photomask as described in claim 1, characterized in that, The step of forming a mask layer filling each of the first windows on the surface of the metal seed layer facing the first window by an electroforming process includes: The metal seed layer is electrically connected to the electroforming cathode, and the Invar alloy material is electrically connected to the electroforming anode; The silicon substrate on which the metal seed layer is formed is placed in the electroforming solution; The electroformed cathode and the electroformed anode are energized for a preset time to obtain the mask layer.

3. The method for fabricating a photomask as described in claim 2, characterized in that, The step of electrically connecting the metal seed layer to the electroforming cathode includes: Provide conductive carriers; The silicon substrate is placed into the conductive carrier, so that the metal seed layer is in contact with the conductive carrier; The conductive carrier is electrically connected to the electroformed cathode.

4. The method for fabricating a photomask as described in any one of claims 1 to 3, characterized in that, The step of forming a plurality of first windows on the surface of the first photoresist layer that expose a portion of the metal seed layer includes: Provide photomasks; Multiple light-transmitting openings are formed on the surface of the photomask; The photomask is used to expose and develop the surface of the first photoresist layer, so that the first photoresist layer forms a first window between every two adjacent light-transmitting holes.

5. The method for fabricating a photomask as described in any one of claims 1 to 3, characterized in that, The step of removing the first photoresist layer, the silicon substrate, and the metal seed layer includes: Remove the first photoresist layer to form multiple openings on the surface of the mask layer; A second photoresist layer is formed on the side of the silicon substrate opposite to the metal seed layer; The second photoresist layer is exposed and developed; The first etched area of ​​the silicon substrate covering each of the openings of the mask layer and the second etched area of ​​the metal seed layer covering each of the openings of the mask layer are sequentially etched to form a support frame composed of the silicon substrate and the metal seed layer.

6. The method for fabricating a photomask as described in claim 5, characterized in that, After the step of removing the first photoresist layer to form a plurality of openings on the surface of the mask layer, and before the step of forming a second photoresist layer on the side of the silicon substrate opposite to the metal seed layer, the method further includes: A third photoresist layer is formed on the surface of the mask layer and the metal seed layer, the third photoresist layer covering the surface of the mask layer and filling each of the openings.

7. The method for fabricating a photomask as described in claim 6, characterized in that, Following the step of etching the second etched region of the metal seed layer that covers each of the openings of the mask layer, the method further includes: Remove the second and third photoresist layers.

8. A photomask, characterized in that, The mask includes: Supporting framework; A mask layer is disposed on the support frame, and the surface of the mask layer has multiple openings for passing through the deposition material during OLED pixel layer deposition to form the OLED pixel layer.

9. The photomask as described in claim 8, characterized in that, The opening has a rectangular cross-sectional shape and a width of L, where 2µm ≤ L ≤ 15µm.

10. The photomask as claimed in any one of claims 8 or 9, characterized in that, The support frame is disposed along the edge of the mask layer and located on one side of the mask layer; the support frame includes a metal seed layer and a silicon substrate stacked sequentially in a direction perpendicular to the mask layer, and the metal seed layer is located on the surface of the mask layer.

11. The photomask as described in claim 10, characterized in that, The metal seed layer includes a nickel layer and an aluminum layer stacked sequentially in a direction perpendicular to the mask layer, with the nickel layer located on the surface of the silicon substrate.

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