Step seed-based microlens and preparation method therefor

Abstract

The present invention relates to the technical field of semiconductors. Disclosed are a step seed-based microlens and a preparation method therefor. The microlens comprises: a step seed structure comprising a bottom planar layer and a top seed layer arranged on the bottom planar layer, wherein the length of the top seed layer is less than that of the bottom planar layer, so that a step difference is formed between the top seed layer and the bottom planar layer; and a microlens shell layer arranged around the step seed structure, wherein the microlens shell layer is made of an inorganic transparent material, and the microlens shell layer protrudes in the direction away from the bottom planar layer. According to the technical solution provided by the present application, a microlens shell layer of a required shape can be formed on the basis of the designed step seed structure, the process is simple, and the yield is guaranteed.

Description

Microlens based on step seeds and preparation method thereof

[0001] This application claims priority to Chinese patent application No. 2023116806905, filed on December 8, 2023, entitled “Microlens based on step seeds and preparation method thereof,” the entire contents of which are incorporated herein by reference. Technical Field

[0002] The present invention relates to the field of semiconductor technology, and in particular to a step seed-based microlens and a preparation method thereof. Background Art

[0003] As an important optical component, microlens has attracted a lot of attention due to its small size, light weight and high integration.

[0004] With the development of the semiconductor industry, a series of microlens fabrication methods have emerged. Traditional microlens fabrication methods include photoresist reflow, etching, printing, laser direct writing, dot wetting, and nanoimprinting. These traditional microlens fabrication methods are complex and prone to yield issues. To simplify microlens fabrication, deposition can be used, which has a relatively simple overall process.

[0005] However, if deposition is performed directly on the outer surface of the pixel unit, for example, chemical vapor deposition, a suitable microlens shape cannot be obtained. Therefore, a solution is urgently needed to structure the device so that a microlens that meets the shape requirements can be obtained during the deposition process. Summary of the Invention

[0006] The object of the present invention is to provide a step seed-based microlens and a preparation method thereof, which can form a microlens shell layer that meets shape requirements on the basis of the step seed structure, with a relatively simple process and guaranteed yield.

[0007] In order to achieve the above-mentioned object of the invention, the present invention proposes the following technical solutions:

[0008] In one aspect, a step seed-based microlens is provided, the microlens comprising:

[0009] a step seed structure comprising a bottom planar layer and a top seed layer disposed above the bottom planar layer, wherein the top seed layer is shorter than the bottom planar layer so that a step difference is formed between the top seed layer and the bottom planar layer;

[0010] A microlens shell layer is arranged around the outer periphery of the step seed structure. The microlens shell layer is made of an inorganic transparent material and is convex in a direction away from the bottom plane layer.

[0011] In a possible implementation, the step seed structure is a pixel structure, and the pixel structure includes: a pixel unit and a CMOS layer at the bottom of the pixel unit;

[0012] At least one top layer in the pixel structure serves as the top seed layer, and at least one bottom layer in the pixel structure serves as the bottom planar layer.

[0013] In a possible implementation, the top seed layer includes the compound pixel layer in the pixel unit, and the bottom planar layer includes the ohmic layer, the bonding layer, and the COMS layer in the pixel unit;

[0014] or;

[0015] The top seed layer includes a compound pixel layer, an ohmic layer, and a bonding layer in the pixel unit, and the bottom planar layer includes a CMOS layer at the bottom of the pixel unit.

[0016] In one possible implementation, the step seed structure is a pixel structure with a filling layer, the pixel structure with a filling layer includes: a pixel unit, a CMOS layer at the bottom of the pixel unit, and a filling layer on the top of the pixel unit, wherein the filling layer is made of a high-temperature resistant organic material or an inorganic dielectric material;

[0017] At least one top layer in the pixel structure with the filling layer serves as the top seed layer, and at least one bottom layer in the pixel structure with the filling layer serves as the bottom plane layer.

[0018] In a possible implementation, the top seed layer includes the filling layer in the pixel structure having the filling layer, and the bottom plane layer includes the pixel unit and the CMOS layer in the pixel structure having the filling layer.

[0019] In one possible implementation, the size of the filling layer gradually decreases in a direction away from the CMOS layer. In one possible implementation, the filling layer includes: a first filling layer on top of the pixel unit, a second filling layer on top of the first filling layer, and the length of the second filling layer is less than the length of the first filling layer; the top seed layer includes the second filling layer in the pixel structure with the filling layer; and the bottom planar layer includes the first filling layer, the pixel unit, and the CMOS layer in the pixel structure with the filling layer.

[0020] In a possible implementation manner, a central axis of the filling layer and a central axis of the pixel unit are aligned.

[0021] In a possible implementation, the pixel unit further includes a passivation layer covering the sidewall.

[0022] In a possible implementation, the surface of the passivation layer and the top surface of the pixel unit are further covered with a common cathode layer.

[0023] In a possible implementation, the step difference is between 0.5 μm and 10 μm.

[0024] In a possible implementation, a bottom diameter of the top seed layer is between 0.5 μm and 10 μm.

[0025] In a possible implementation, a ratio of the step difference to a bottom diameter of the top seed layer is between 0.5 and 3.

[0026] In a possible implementation, the height of the microlens shell layer is 0.5 to 3 times the diameter of the microlens shell layer.

[0027] In a possible implementation, the diameter of the microlens shell layer is 0.8 to 1 times the center distance between adjacent pixel units.

[0028] In a possible implementation, a bottom diameter of the top seed layer is 0.4 to 0.8 times the center distance between adjacent pixel units.

[0029] In one possible implementation, the shape of the top seed layer includes:

[0030] Cylindrical, pyramidal, conical, and polygonal pyramid.

[0031] In a possible implementation, the shape of the microlens shell layer includes: hemispherical, semi-rugby ball shape.

[0032] In another aspect, a method for preparing a microlens is provided, wherein the method is used to prepare the microlens according to the above aspect, and the method comprises:

[0033] preparing a stepped seed structure, the stepped seed structure comprising a bottom planar layer and a top seed layer disposed above the bottom planar layer, wherein the top seed layer is shorter than the bottom planar layer so that a step difference is formed between the top seed layer and the bottom planar layer;

[0034] Chemical vapor deposition is performed using the step difference to form a microlens shell layer that is in-situ grown around the step seed structure. The microlens shell layer is convex in a direction away from the bottom plane layer and is made of an inorganic transparent material.

[0035] In a possible implementation, the step seed structure preparation includes:

[0036] Graphically etching pixel units;

[0037] The compound pixel layer in the patterned pixel unit is used as the top seed layer, and the ohmic layer, bonding layer and COMS layer at the bottom of the pixel unit are used as the bottom planar layer;

[0038] or;

[0039] The compound pixel layer, the ohmic layer and the bonding layer in the patterned pixel unit are used as the top seed layer, and the CMOS layer at the bottom of the patterned pixel unit is used as the bottom plane layer.

[0040] In a possible implementation, the step seed structure preparation includes:

[0041] Graphically etching pixel units;

[0042] Filling the top of the patterned pixel unit to form a filling layer, wherein the filling layer is made of a high-temperature resistant organic material or an inorganic dielectric material;

[0043] Patterned photolithography uses the filling layer of the high-temperature resistant organic material, or patterned etching uses the filling layer of the inorganic dielectric material, so that the length of the patterned filling layer is less than the length of the top of the pixel unit, the filling layer is used as the top seed layer, and the pixel unit and COMS layer are used as the bottom plane layer;

[0044] or,

[0045] Patterned lithography uses the filling layer of the high-temperature resistant organic material, or patterned etching uses the filling layer of the inorganic dielectric material, so that the patterned filling layer forms a first filling layer above the top of the pixel unit and a second filling layer above the first filling layer, and the length of the second filling layer is less than the length of the first filling layer, and the second filling layer is used as the top seed layer, and the first filling layer, the pixel unit and the COMS layer are used as the bottom plane layer.

[0046] In a possible implementation, after patterning and etching the pixel unit, the method further includes:

[0047] Passivating the sidewalls of the pixel unit to form a passivation layer;

[0048] A transparent conductive film is coated on the surface of the passivation layer and the top surface of the pixel unit to form a common cathode layer.

[0049] In a possible implementation, performing chemical vapor deposition using the step difference to in-situ grow a microlens shell layer around the step seed structure includes:

[0050] The size and shape of the microlens shell layer formed by in-situ growth around the step seed structure by chemical vapor deposition are controlled by step seed related parameters including the step difference and in-situ growth process parameters.

[0051] Compared with the prior art, the present invention has the following beneficial effects:

[0052] During device construction, a step seed structure is formed. The step seed structure includes a bottom plane layer and a top seed layer disposed above the bottom plane layer. The length of the top seed layer is smaller than that of the bottom plane layer, so that a step difference is formed between the top seed layer and the bottom plane layer. A microlens shell layer is thus formed on the step seed structure. Based on the arrangement of the step seed layer, the microlens shell layer can naturally bulge in a direction away from the bottom plane layer, thereby obtaining the desired microlens.

[0053] Furthermore, the microlens shell layer formed by in-situ growth is made of an inorganic transparent material, which is easier to overcome the tests of high temperature and mechanical deformation than organic materials.

[0054] Furthermore, the size and morphology of the microlens are also controlled by the design of the step seed structure, without the need for separate preparation of imprint templates or other changes, making mass production operations convenient. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] FIG1 is a schematic structural diagram of a microlens provided in an embodiment of the present application;

[0056] FIG2 is a schematic structural diagram of a microlens provided in an embodiment of the present application;

[0057] FIG3 is a schematic diagram of the structure of a microlens provided in an embodiment of the present application;

[0058] FIG4 is a schematic diagram of the structure of a microlens provided in an embodiment of the present application;

[0059] FIG5 is a schematic structural diagram of a pixel unit provided in an embodiment of the present application;

[0060] FIG6 is a schematic structural diagram of a pixel unit provided in an embodiment of the present application;

[0061] FIG7 is a schematic structural diagram of a filled pixel unit provided in an embodiment of the present application;

[0062] FIG8 is a schematic structural diagram of a filled pixel unit provided in an embodiment of the present application;

[0063] FIG9 is a schematic structural diagram of a filled pixel unit provided in an embodiment of the present application;

[0064] FIG10 is a schematic structural diagram of a pixel unit provided in an embodiment of the present application;

[0065] FIG11 is a flow chart of a method for preparing a microlens provided in an embodiment of the present application;

[0066] FIG12 is a schematic diagram of light-emitting parameters of a structure without a microlens provided in an embodiment of the present application;

[0067] FIG13 is a schematic diagram of light-emitting parameters of a microlens structure provided in an embodiment of the present application. DETAILED DESCRIPTION

[0068] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0069] In the description of the present invention, it should be understood that the orientations or positional relationships indicated by terms such as "vertical", "upper", "lower", "top", "side", "inside", and "outside" are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0070] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0071] Traditional microlens preparation methods have many drawbacks, such as:

[0072] (1) Microlenses are prepared using a photoresist melting scheme. In this scheme, all lenses are organic structures, and the material's temperature resistance and mechanical deformation resistance are poor; for example, patent CN117008226A.

[0073] (2) The microlens is prepared by an imprinting scheme. In this scheme, the lens is also an organic structure. In addition to the poor temperature resistance and mechanical properties of the material, an additional imprinting template needs to be prepared. The process is relatively cumbersome, and yield problems such as adhesion are prone to occur during demolding after imprinting; such as patents CN1977189A and CN114913558A.

[0074] (3) Microlenses are prepared using an etching scheme, combined with a photoresist melting scheme to prepare the microlens morphology, and the microlens morphology is transferred to quartz using an etching transfer pattern. This scheme has high process requirements and is relatively complex. The melt etching structure is prone to lens deformation, resulting in yield problems; such as patent CN115343788A.

[0075] To avoid the above problems, in an embodiment of the present application, a technical solution is proposed in which a microlens shell layer is formed by depositing an inorganic oxide or oxynitride using a step seed structure as a guide. The microlens shell layer can be formed into a desired shape based on the design of the step seed structure.

[0076] First, the specific structure of the microlens proposed in this application will be described.

[0077] The present invention provides a step seed-based microlens (hereinafter referred to as a microlens), as shown in FIG1 , which includes:

[0078] The step seed structure includes a bottom plane layer and a top seed layer arranged above the bottom plane layer, and the length of the top seed layer is smaller than that of the bottom plane layer, so that a step difference is formed between the top seed layer and the bottom plane layer; a microlens shell layer is arranged around the outside of the step seed structure, the microlens shell layer is an inorganic transparent material, and the microlens shell layer protrudes in the direction away from the bottom plane layer.

[0079] In the embodiment of the present application, the formation of the microlens utilizes a step seed structure. The step seed structure refers to a seed structure with a step pattern, which can be divided into a bottom plane layer and a top seed layer arranged above the bottom plane. Since the length of the top seed layer is shorter than the length of the bottom plane layer, the two layers constitute a step pattern with a step difference.

[0080] Based on the design of a stepped seed structure, chemical vapor deposition (CVD) is performed with the top seed layer as the center to in-situ grow a microlens shell layer made of an inorganic transparent material. Due to the step difference, the shell layer in-situ grown from the top seed layer toward the top is significantly thicker than the shell layer in-situ grown toward the sides. As a result, the microlens shell layer naturally bulges away from the bottom planar layer, resulting in the desired convex microlens shell layer.

[0081] Furthermore, the ratio of the step difference to the bottom diameter of the top seed layer is between 0.5 and 3. Under the design that the ratio of the step difference to the bottom diameter of the top seed layer is between 0.5 and 3, the protrusion of the microlens shell layer also adapts to this limitation to form the desired protrusion shape.

[0082] The microlens shell layer can be specifically made of inorganic transparent dielectric layer materials such as silicon oxide, silicon nitride, aluminum oxide, etc. The thickness of the microlens made based on the step seed can be equal to the thickness of the top seed layer plus the thickness of the microlens shell layer.

[0083] It can be understood that since the top seed layer and the bottom plane layer may have different lengths at different heights, the length of the top seed layer is smaller than the length of the bottom plane layer, which can specifically mean that the longest length of the top seed layer is smaller than the shortest length of the bottom plane layer.

[0084] The step difference is between 0.5 μm and 10 μm, within which a microlens shell layer that meets the required height can be formed.

[0085] The bottom diameter of the top seed layer is between 0.5 μm and 10 μm, within which a microlens shell layer with a surface width that meets the requirements can be formed.

[0086] Furthermore, the bottom diameter of the top seed layer is 0.4 to 0.8 times the center distance between adjacent pixel units. Based on the top seed layer in this size range, a matching microlens shell layer is obtained. This microlens shell layer can correspond to each pixel unit one-to-one and can also cover the pixel unit to achieve a better optical collimation effect.

[0087] Among them, the step seed structure can be formed by a separate pixel unit, as shown in Figure 2, using a pixel structure including a pixel unit and a CMOS layer to form a step seed structure to form a microlens; it can also be further formed by a pixel structure filled with a filling layer. The filling layer can be made of a high-temperature resistant organic material (≥200°C) such as SU8, silica gel, polyimide, etc., or an inorganic dielectric material such as silicon oxide, as shown in Figure 3 or Figure 4, using a pixel structure filled with a filling layer to form a step seed structure to form a microlens.

[0088] In a possible implementation, the step seed structure is a pixel structure; at least one top layer in the pixel structure serves as a top seed layer, and at least one bottom layer in the pixel structure serves as a bottom planar layer.

[0089] In this implementation, a step seed structure is formed by a separate pixel structure, at least one top layer in the pixel structure is used as a top seed layer, and at least one bottom layer in the pixel structure is used as a bottom planar layer.

[0090] Further, based on the above implementation method, the top seed layer includes the compound pixel layer in the pixel unit, and the bottom planar layer includes the ohmic layer, the bonding layer and the COMS layer at the bottom of the pixel unit in the pixel unit; or; the top seed layer includes the compound pixel layer, the ohmic layer and the bonding layer in the pixel unit, and the bottom planar layer includes the COMS layer at the bottom of the pixel unit.

[0091] That is, as shown in Figures 5 and 6, the pixel unit includes: a compound pixel layer, an ohmic layer, a bonding layer, and the pixel unit and the COMS layer form a pixel structure. When forming a step seed structure through a separate pixel structure, one possible way is: as shown in Figure 5, the compound pixel layer in the pixel unit is patterned and etched as a top seed layer, and the other layers in the pixel unit, namely the ohmic layer, the bonding layer, and the bottom COMS layer, are used as the bottom plane layer; another possible way is: as shown in Figure 6, the compound pixel layer and the bonding layer in the pixel unit are patterned and etched to form a whole, and this whole is used as the top seed layer, and the other layers in the pixel structure, namely the COMS layer, are used as the bottom plane layer. It can be understood that forming a step seed structure in this way is relatively simple to implement.

[0092] In one possible implementation, the step seed structure is a pixel structure with a filling layer composed of a pixel unit, a filling layer filled on the top of the pixel unit, and a CMOS layer at the bottom of the pixel unit, and the filling layer is made of high-temperature resistant organic material or inorganic dielectric material; at least one top layer in the pixel structure with a filling layer serves as a top seed layer, and at least one bottom layer in the pixel structure with a filling layer serves as a bottom plane layer.

[0093] In this implementation, as shown in Figure 7, a high-temperature resistant organic material or an inorganic dielectric material (such as silicon oxide) is filled on the top of the prepared pixel unit to form a pixel structure with a filling layer. This pixel structure with a filling layer has a step seed structure, and at least one top layer in the pixel structure with a filling layer is used as a top seed layer, and at least one bottom layer in the pixel structure with a filling layer is used as a bottom plane layer.

[0094] Furthermore, based on the above implementation, the top seed layer includes a filling layer, and the bottom planar layer includes pixel units and a CMOS layer. Furthermore, the filling layer can gradually decrease in size away from the CMOS layer, thereby enabling the corresponding microlens shell layer to have a convex shape. Furthermore, the central axis of the filling layer and the central axis of the pixel unit are aligned, so that the central axis of the subsequent microlens shell layer can be aligned with the central axis of the final pixel unit, thereby better realizing the function of the microlens shell layer.

[0095] Furthermore, the filling layer includes: a first filling layer above the top of the pixel unit; a second filling layer above the first filling layer, wherein the length of the second filling layer is shorter than that of the first filling layer; the top seed layer includes the second filling layer in the filled pixel unit; and the bottom planar layer includes the first filling layer, the pixel unit, and the CMOS layer in the filled pixel unit. Furthermore, the central axes of the first filling layer, the second filling layer, and the pixel unit are aligned, so that the central axis of the subsequent microlens shell layer can be aligned with the central axis of the final pixel unit, thereby better realizing the function of the microlens shell layer.

[0096] That is, when forming a step seed structure using pixel cells filled with a filling layer, one possible approach is: as shown in FIG8 , the filling layer is patterned so that its length is less than the length of the top of the pixel cell, the filling layer is used as the top seed layer, and the pixel cell and CMOS layer are used as the bottom planar layer. The microlens prepared by the step seed structure corresponding to FIG8 is shown in FIG3 . Another possible approach is: as shown in FIG9 , the filling layer is patterned to form a first filling layer and a second filling layer from bottom to top, the length of the second filling layer being less than the length of the first filling layer, the second filling layer is used as the top seed layer, and the remaining first filling layer, pixel cell, and CMOS layer are used as the bottom planar layer. The microlens prepared by the step seed structure corresponding to FIG9 is shown in FIG4 . It can be understood that forming a step seed structure in this manner is not restricted by the shape of the pixel cell, and the shape, diameter, height, and other structural parameters of the top seed layer can be more flexibly controlled to obtain the desired microlens shell layer based on this top seed layer.

[0097] Furthermore, the center distance between two adjacent pixel units is defined as Pitch. In the design of using the filling layer as the top seed layer, the projected diameter of the top seed layer on the CMOS layer can be controlled to be 0.4 to 0.8 times the Pitch, and the height is controlled to be 0.5 to 3 times the diameter of the top seed layer. This ensures that the diameter of the final microlens shell layer is controlled to be 0.8 to 1 times the Pitch, and the height of the microlens shell layer is 0.5 to 3 times the diameter of the microlens shell layer, thereby obtaining the desired microlens shell layer.

[0098] It is understandable that, as shown in the above two implementation methods, the step seed structure required by this application can be implemented using a conventional step difference scheme, such as directly patterning organic materials through photolithography, such as SU8, silica gel, polyimide and other high-temperature resistant organic materials, and can be formed by etching inorganic materials, such as the need to form a compound pixel layer for display, subsequent growth of inorganic dielectric materials, etc. The step seed scheme for preparing microlenses does not require complex processes such as melting, imprinting, and laser direct writing, nor does it require the traditional process of melting the microlens morphology mask and then etching. It does not need to ensure that the melting and etching consistency requirements are very high, and the process is simple and the yield is high. In addition, compared with seed structures based on other shapes, such as hemispherical seed structures, the step seed scheme for preparing microlenses does not require hot-melt mask layers to hemispherical shapes or debugging etching processes to control hemispherical etching. Therefore, the control accuracy is higher, the process is simple, and the feasibility is higher.

[0099] In a possible implementation, the pixel unit further includes a passivation layer covering the sidewall.

[0100] In this implementation, as shown in Figure 10, a passivation layer is formed on the sidewall surface of the pixel unit to passivate and protect the pixel unit. The passivation layer can be a single layer or a stack of dielectric layers such as aluminum oxide, silicon nitride, or silicon oxide.

[0101] In a possible implementation, the surface of the passivation layer and the top surface of the pixel unit are further covered with a common cathode layer.

[0102] In this implementation, as shown in FIG10 , a common cathode layer is further formed on the surface of the passivation layer and the top surface of the pixel unit to complete the common cathode preparation of the pixel unit. The common cathode layer can be made of a transparent conductive film, which can be a combination of one or more of an ITO (Indium Tin Oxide) film, an AZO (Antimony Doped Zinc Oxide) film, an ATO (Antimony Doped Tin Oxide) film, and an FTO (Fluorine Doped Tin Oxide) film. The transparent conductive film can also be formed by plating a thin metal (such as Al, Au, Ag) on ​​the surface of ITO and then annealing it to form metal-doped ITO, so as to enhance the current transmission capability of the common cathode layer.

[0103] In one possible implementation, the shape of the top seed layer includes: cylindrical, prism-shaped, conical, and polygonal pyramidal. That is, the shape of the top seed layer in the step seed structure can be set to cylindrical, prism-shaped, conical, polygonal pyramidal (such as hexagonal, octagonal, etc.) as needed during the patterning process.

[0104] In a possible implementation, the shape of the microlens shell includes: hemispherical and semi-rugby ball shapes. That is, the microlens shell formed by in-situ growth can be configured as a hemispherical microlens or a semi-rugby ball shaped microlens shell as needed.

[0105] In summary, the microlens provided in the embodiments of the present application forms a step seed structure during device construction. This step seed structure includes a bottom plane layer and a top seed layer disposed above the bottom plane layer. The top seed layer is shorter than the bottom plane layer, so that a step difference is formed between the top seed layer and the bottom plane layer. A microlens shell layer is thus formed on this step seed structure. Based on the arrangement of the step seed layer, this microlens shell layer can naturally bulge away from the bottom plane layer, thereby obtaining the desired microlens.

[0106] Furthermore, the microlens shell layer formed by in-situ growth is made of an inorganic transparent material, which is easier to overcome the tests of high temperature and mechanical deformation than organic materials.

[0107] Next, a method for preparing the microlens corresponding to the microlens described in the above embodiment will be described.

[0108] The present application also provides a method for preparing a microlens. The method is used to prepare the microlens described in the above embodiment. As shown in FIG11 , the method may include the following steps:

[0109] Step 1110: Prepare a step seed structure, which includes a bottom plane layer and a top seed layer arranged above the bottom plane layer, and the length of the top seed layer is smaller than the length of the bottom plane layer, so that a step difference is formed between the top seed layer and the bottom plane layer.

[0110] In this step, a step seed structure with a step difference is prepared. The step seed structure includes a bottom plane layer and a top seed layer. The length of the top seed layer is prepared to be smaller than that of the bottom plane layer, thereby forming a step difference.

[0111] In one possible implementation, step 1110 includes:

[0112] (1) Graphically etched pixel units.

[0113] Specifically, for the pixel unit structure shown in FIG. 5 and FIG. 6 , the compound pixel layer, the ohmic layer, and the bonding layer are patterned and etched in order from top to bottom.

[0114] (2.1) The compound pixel layer in the patterned pixel unit is used as the top seed layer, and the ohmic layer, bonding layer and the COMS layer at the bottom of the patterned pixel unit are used as the bottom planar layer.

[0115] As shown in Figure 5, under the design that the length of the compound pixel layer after patterning etching is smaller than the length of the ohmic layer, the bonding layer, and the COMS layer, the compound pixel layer in the patterned pixel unit is used as the top seed layer, and the ohmic layer, the bonding layer, and the COMS layer at the bottom of the patterned pixel unit are used as the bottom planar layer, thereby preparing a step seed structure.

[0116] (2.2) The compound pixel layer, ohmic layer and bonding layer in the patterned pixel unit are used as the top seed layer, and the COMS layer at the bottom of the patterned pixel unit is used as the bottom plane layer.

[0117] As shown in FIG6 , in a design where the length of the compound pixel layer, the ohmic layer, and the bonding layer formed by patterned etching is shorter than the length of the COMS layer, the compound pixel layer, the ohmic layer, and the bonding layer in the patterned pixel unit are used as the top seed layer, and the COMS layer is used as the bottom planar layer, thereby preparing a step seed structure.

[0118] In one possible implementation, step 1110 includes:

[0119] (1) Graphically etched pixel units.

[0120] Specifically, for the pixel unit structure shown in FIG. 5 and FIG. 6 , the compound pixel layer, the ohmic layer, the bonding layer, and the CMOS layer are patterned and etched in order from top to bottom.

[0121] (2) Filling is performed on the top of the patterned pixel unit to form a filling layer, and the filling layer is made of high-temperature resistant organic material or inorganic dielectric material.

[0122] Specifically, the pixel unit is filled with a high-temperature resistant organic or inorganic dielectric material (such as silicon oxide), specifically, the top of the pixel unit is filled.

[0123] (3.1) Patterned photolithography uses a filling layer of high-temperature resistant organic material, or patterned etching uses a filling layer of inorganic dielectric material, so that the length of the patterned filling layer is less than the length of the top of the pixel unit, and the filling layer is used as the top seed layer, and the pixel unit and CMOS layer are used as the bottom planar layer.

[0124] As shown in Figures 7 and 8, for a filled pixel unit consisting of a pixel unit and a filling layer, if the filling layer is made of a high-temperature resistant organic material, the filling layer is patterned by photolithography; if the filling layer is made of an inorganic dielectric material, the filling layer is patterned by etching, so that the length of the patterned filling layer is smaller than the length of the top of the pixel unit, the filling layer is used as the top seed layer, and the pixel unit and the CMOS layer are used as the bottom planar layer, thereby preparing a step seed structure.

[0125] (3.2) Patterned photolithography uses a filling layer of high-temperature resistant organic material, or patterned etching uses a filling layer of inorganic dielectric material, so that the patterned filling layer forms a first filling layer above the top of the pixel unit and a second filling layer above the first filling layer, and the length of the second filling layer is less than the length of the first filling layer. The second filling layer is used as the top seed layer, and the first filling layer, pixel unit, and CMOS layer are used as the bottom planar layer.

[0126] As shown in Figures 7 and 9, for a filled pixel unit composed of a pixel unit and a filling layer, if the filling layer uses a high-temperature resistant organic material, the filling layer is patterned by photolithography; if the filling layer uses an inorganic dielectric material, the filling layer is patterned by etching, so that the patterned filling layer is divided into a first filling layer and a second filling layer, the length of the second filling layer is smaller than the length of the first filling layer, the second filling layer is used as the top seed layer, and the first filling layer, the pixel unit, and the CMOS layer are used as the bottom planar layer, thereby preparing a step seed structure.

[0127] In one possible implementation, after the graphic etching of the pixel unit in the above step, the method further includes the following steps: passivating the side walls of the pixel unit to form a passivation layer; and covering the surface of the passivation layer and the top surface of the pixel unit with a transparent conductive film to form a common cathode layer.

[0128] In this step, after the patterned etching of the pixel unit is completed, compound pixel sidewall passivation and common cathode current expansion are further introduced to complete the preparation of N-type ohmic contact and common cathode.

[0129] Step 1120: chemical vapor deposition is performed using the step difference to in-situ grow a microlens shell layer around the step seed structure. The microlens shell layer is convex in a direction away from the bottom plane layer and is made of an inorganic transparent material.

[0130] In this step, the pre-prepared step seed structure is used as a guide, and the inorganic silicon oxide or nitride oxide prepared by the PSG (phosphate glass), BPSG (borophosphosilicate glass) process or the deposition source such as TEOS (tetraethoxysilane), TEPO (triethyl phosphate) has the characteristics of fluidity, and the deposited inorganic transparent material is naturally grown into a microlens structure.

[0131] In one embodiment, taking a Micro-LED microdisplay chip as an example, after in-situ growth of microlenses, the luminous intensity increased by 80%, and the luminous angle converged from 110° (as shown in FIG12 , without microlenses) to 51° (as shown in FIG13 , with in-situ growth of microlenses).

[0132] In one possible implementation, step 920 includes controlling the size and shape of a microlens shell layer formed by in-situ growth around the step seed structure via chemical vapor deposition using step seed-related parameters including step difference and in-situ growth process parameters.

[0133] In this step, the size and shape of the microlens shell layer formed are related to the step seed-related parameters and in-situ growth process parameters. Step seed-related parameters refer to parameters related to the step seed structure, such as the step height and the dimensions of the top seed layer (e.g., height, bottom length, and top length). In-situ growth process parameters refer to parameters involved in the chemical vapor deposition (CVD) in-situ growth process, such as whether a high-temperature annealing process is used.

[0134] In one embodiment, a semi-rugby ball-shaped microlens can be fabricated by preparing a stepped seed structure with a conical top seed layer. If necessary, the semi-rugby ball-shaped microlens can be reflowed to a hemispherical shape through subsequent high-temperature annealing and continued flow. A semi-rugby ball microlens can be obtained by preparing a top seed layer with a bottom diameter of 2 μm, a top diameter of 1.6 μm, and a height of 1.5 μm, followed by CVD growth of a 1 μm PSG layer. This can then be annealed in a nitrogen environment at 500°C to 800°C for 2 hours to obtain a hemispherical microlens.

[0135] It is understandable that after the microlens shell layer is formed based on this solution, the microlens shell layer may be further processed to precisely control the shape of the microlens shell layer, and this application does not impose any limitation on this.

[0136] In summary, the microlens fabrication method provided in the embodiments of the present application can prepare a step seed structure based on a conventional step difference scheme, and directly perform chemical vapor deposition on the step seed structure to form a microlens by in-situ growth. The overall process does not require complex special melting and special etching techniques, reducing process difficulty and complexity, achieving good compatibility with semiconductor processes, and ensuring low cost and high mass production yield.

[0137] Furthermore, the microlens shell layer formed by in-situ growth is made of an inorganic transparent material, which is easier to overcome the tests of high temperature and mechanical deformation than organic materials.

[0138] Furthermore, during the preparation process of the microlens, the size and morphology of the microlens can be flexibly controlled through the design of the step seed structure and in-situ growth processes such as high-temperature annealing, without the need for changes such as the separate preparation of the imprint template, making mass production operations convenient.

[0139] All of the above optional technical solutions can be combined in any way to form optional embodiments of the present invention, that is, any multiple embodiments can be combined to meet the needs of different application scenarios. They are all within the scope of protection of this application and will not be described in detail here.

[0140] It should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A step seed-based microlens, characterized in that: The microlens comprises: A step seed structure, the step seed structure comprising a bottom plane layer and a top seed layer disposed on the bottom plane layer, wherein the length of the top seed layer is smaller than the length of the bottom plane layer, so that a step difference is formed between the top seed layer and the bottom plane layer; A microlens shell layer is arranged around the outer periphery of the step seed structure, wherein the microlens shell layer is made of an inorganic transparent material and protrudes in a direction away from the bottom plane layer.

2. The microlens according to claim 1, characterized in that: The step seed structure is a pixel structure, and the pixel structure includes: a pixel unit and a CMOS layer at the bottom of the pixel unit; At least one top layer in the pixel structure serves as the top seed layer, and at least one bottom layer in the pixel structure serves as the bottom plane layer.

3. The microlens according to claim 2, characterized in that: The top seed layer includes the compound pixel layer in the pixel unit, and the bottom plane layer includes the ohmic layer, the bonding layer and the COMS layer in the pixel unit; or; The top seed layer includes a compound pixel layer, an ohmic layer and a bonding layer in the pixel unit, and the bottom plane layer includes a COMS layer at the bottom of the pixel unit.

4. The microlens according to claim 1, characterized in that: The step seed structure is a pixel structure with a filling layer, and the pixel structure with a filling layer includes: a pixel unit, a CMOS layer at the bottom of the pixel unit, and a filling layer at the top of the pixel unit, and the filling layer is made of a high temperature resistant organic material or an inorganic dielectric material; At least one top layer in the pixel structure with the filling layer serves as the top seed layer, and at least one bottom layer in the pixel structure with the filling layer serves as the bottom plane layer.

5. The microlens according to claim 4, characterized in that: The top seed layer includes the filling layer in the pixel structure with the filling layer, and the bottom plane layer includes the pixel unit and the CMOS layer in the pixel structure with the filling layer.

6. The microlens according to claim 5, characterized in that: The filling layer gradually decreases in size along a direction away from the CMOS layer.

7. The microlens according to claim 4, characterized in that: The filling layer comprises: A first filling layer is provided on the top of the pixel unit, and a second filling layer is provided on the first filling layer, wherein the length of the second filling layer is less than the length of the first filling layer, the top seed layer includes the second filling layer in the pixel structure having the filling layer, and the bottom plane layer includes the first filling layer in the pixel structure having the filling layer, the pixel unit, and the CMOS layer.

8. The microlens according to claim 4, characterized in that: The central axis of the filling layer and the central axis of the pixel unit are aligned.

9. The microlens according to claim 2 or 4, characterized in that: The pixel unit further includes a passivation layer covering the side wall.

10. The microlens according to claim 8, characterized in that: The surface of the passivation layer and the top surface of the pixel unit are also covered with a common cathode layer.

11. The microlens according to claim 1, characterized in that: The step difference is between 0.5 μm and 10 μm.

12. The microlens according to claim 1, characterized in that: The bottom diameter of the top seed layer is between 0.5 μm and 10 μm.

13. The microlens according to claim 1, characterized in that: The bottom diameter of the top seed layer is 0.4 to 0.8 times the center distance between adjacent pixel units.

14. The microlens according to claim 1, characterized in that: A ratio of the step difference to the bottom diameter of the top seed layer is between 0.5 and 3.

15. The microlens according to claim 1, characterized in that: The height of the microlens shell layer is 0.5 to 3 times the diameter of the microlens shell layer.

16. The microlens according to claim 1, characterized in that: The diameter of the microlens shell layer is 0.8 to 1 times the center distance between adjacent pixel units.

17. The microlens according to claim 1, characterized in that: The shape of the top seed layer includes: Cylindrical, prism-shaped, cone-shaped, polygonal cone-shaped.

18. The microlens according to claim 1, characterized in that: The shape of the microlens shell layer includes: hemispherical shape and semi-rugby ball shape.

19. A method for preparing a microlens, characterized in that: The method is used to prepare the microlens according to any one of claims 1 to 18, and the method comprises: Prepare a step seed structure, the step seed structure comprising a bottom plane layer and a top seed layer disposed on the bottom plane layer, wherein the length of the top seed layer is smaller than the length of the bottom plane layer, so that a step difference is formed between the top seed layer and the bottom plane layer; Chemical vapor deposition is performed using the step difference to form a microlens shell layer that is in-situ grown around the step seed structure. The microlens shell layer protrudes in a direction away from the bottom plane layer and is made of an inorganic transparent material.

20. The method according to claim 19, characterized in that The step seed structure preparation comprises: Graphically etch pixel units; The compound pixel layer in the patterned pixel unit is used as the top seed layer, and the ohmic layer, bonding layer and COMS layer at the bottom of the pixel unit are used as the bottom plane layer; or; The compound pixel layer, the ohmic layer and the bonding layer in the patterned pixel unit are used as the top seed layer, and the CMOS layer at the bottom of the patterned pixel unit is used as the bottom plane layer.

21. The method according to claim 19, characterized in that The step seed structure preparation comprises: Graphically etch pixel units; Filling the top of the patterned pixel unit to form a filling layer, wherein the filling layer is made of a high temperature resistant organic material or an inorganic dielectric material; Patterned photolithography uses the filling layer of the high temperature resistant organic material, or patterned etching uses the filling layer of the inorganic dielectric material, so that the length of the patterned filling layer is smaller than the length of the top of the pixel unit, the filling layer is used as the top seed layer, and the pixel unit and COMS layer are used as the bottom plane layer; or, Patterned photolithography uses a filling layer of the high-temperature resistant organic material, or patterned etching uses a filling layer of the inorganic dielectric material, so that the patterned filling layer forms a first filling layer on the top of the pixel unit and a second filling layer on the first filling layer, and the length of the second filling layer is less than the length of the first filling layer, and the second filling layer is used as the top seed layer, and the first filling layer, the pixel unit and the CMOS layer are used as the bottom plane layer.

22. The method according to claim 20 or 21, characterized in that After patterning and etching the pixel unit, the method further comprises: Passivating the sidewalls of the pixel unit to form a passivation layer; A transparent conductive film is coated on the surface of the passivation layer and the top surface of the pixel unit to form a common cathode layer.

23. The method according to claim 19, characterized in that The step difference is used to perform chemical vapor deposition to form a microlens shell layer by in-situ growth around the step seed structure, including: The size and shape of the microlens shell layer formed by in-situ growth through chemical vapor deposition around the outside of the step seed structure are controlled by step seed related parameters including the step difference and in-situ growth process parameters.

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