Micro-lens preparation method and micro-lens structure

Abstract

Disclosed in the present invention are a micro-lens preparation method and a micro-lens structure. The micro-lens preparation method comprises: S1, forming, in a first region of a surface of a base material, a first photoresist layer having a specified pattern structure; S2, forming a protective layer on the surface of the base material, and superimposing the protective layer on the first photoresist layer to form a protection structure; S3, forming a metal layer in a third region of the surface of the base material, wherein a second region is in an exposed state, the second region surrounds the first region, and the third region surrounds the second region; and S4, synchronously etching the base material covered with the protection structure and the metal layer on the surface until the specified pattern structure is formed in the first region of the surface of the base material and a recess-shaped structure is formed in the second region. In the present invention, by means of first preparing a photoresist spherical structure on the base material, and then preparing a step structure for supporting a micro-lens, the situation in an existing process of non-uniform photoresist coating caused by first preparing a step structure and then preparing a photoresist spherical lens is avoided, thereby improving the uniformity of a prepared micro-lens and the yield of a product.

Description

Microlens preparation method and microlens structure

[0001] The present invention claims priority to Chinese patent application No. 2024102817881, filed with the Patent Office of China on March 12, 2024, entitled “A method for preparing a microlens and a microlens structure”, the entire contents of which are incorporated herein by reference. Technical Field

[0002] The present invention relates to a microlens preparation method and a microlens structure, belonging to the technical field of micro-optical semiconductor chip manufacturing. Background Art

[0003] A microlens can be a miniature lens ranging in size from one micron to several hundred microns. An array of microlenses arranged in a certain order is called a microlens array. As a commonly used optical device, microlenses (or arrays) can achieve functions such as focusing and collimating light sources, and have important and widespread applications in the field of semiconductor optoelectronics.

[0004] Many microlenses currently feature steps, often called "in-groove products." These steps effectively protect the chip and provide support. Existing processes for creating these steps involve masking them with photoresist. However, due to the poor conformality of photoresist during etching, achieving vertical steps is difficult, which impacts subsequent processing. Another approach involves first creating a metal mask for the steps. However, this process is prone to uneven coating, resulting in varying heights of the resulting adhesive columns, reducing lens uniformity and significantly impacting product yield, wasting resources, and increasing production costs.

[0005] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the present invention aims to provide a microlens preparation method and a microlens structure.

[0007] To achieve the aforementioned object of the invention, the technical solutions adopted by the present invention include:

[0008] The present invention provides a method for preparing a microlens, comprising the following steps:

[0009] S1, forming a first photoresist layer having a specified pattern structure in a first area on the surface of the substrate;

[0010] S2, forming a protective layer on the surface of the substrate, wherein the protective layer is superimposed on the first photoresist layer to form a protective structure;

[0011] S3, forming a metal layer on the third area of ​​the surface of the substrate, with the second area of ​​the surface of the substrate being exposed, the second area surrounding the first area, and the third area surrounding the second area;

[0012] S4. Simultaneously etching the substrate whose surface is covered with the protection structure and the metal layer until the designated graphic structure is formed in a first area on the surface of the substrate and a groove structure is formed in a second area on the surface of the substrate.

[0013] Preferably, the material of the protective layer includes one or a combination of silicon nitride and silicon oxide.

[0014] Preferably, the thickness of the protective layer is 100 nm-200 nm.

[0015] Preferably, step S3 includes:

[0016] S31, forming a second photoresist layer on the first area and the second area of ​​the surface of the substrate, wherein the second photoresist layer partially covers the protective layer and the first photoresist layer;

[0017] S32, forming the metal layer on the surface of the substrate, wherein a portion of the metal layer covers the second photoresist layer;

[0018] S32 , removing the second photoresist layer, and removing a portion of the metal layer covering the second photoresist layer, so that the metal layer is only formed on the third area of ​​the surface of the substrate.

[0019] Preferably, the material of the metal layer includes one or more of Al, Zn, Mo, W, and Ta.

[0020] Preferably, the thickness of the metal layer is 0.5 μm-5 μm.

[0021] Preferably, the metal layer is deposited by electron beam evaporation or sputtering.

[0022] Preferably, the substrate and the photoresist spherical structure are etched using a plasma dry method.

[0023] Preferably, the etching selection ratio is 1:(10-20).

[0024] The present invention also provides a microlens structure, which is manufactured by any of the above-mentioned microlens manufacturing methods.

[0025] Preferably, the microlens structure includes a substrate, a step structure and a microlens, wherein the step structure is a groove-shaped structure formed on the substrate, the microlens is the specified graphic structure and is located on the bottom wall of the step structure, the side wall and the bottom wall of the step structure are perpendicular, and the height of the side wall of the step structure is higher than the height of the microlens.

[0026] Preferably, the step structure is a circular groove structure, and the diameter of the step structure is larger than the diameter of the plane of the microlens.

[0027] Preferably, a plurality of step structures and a plurality of microlenses corresponding to the number of the step structures are provided on the substrate, and the plurality of step structures are regularly distributed on the substrate.

[0028] Preferably, the substrate and the microlens are made of silicon or quartz.

[0029] Compared with the prior art, the advantages of the present invention include:

[0030] The present invention prepares a microlens product with a spherical structure on a substrate first, and then prepares a step structure to support the microlens, thereby effectively avoiding uneven glue spreading, improving the uniformity of the prepared microlens, and further improving the product yield. The method is simple in operation and process and is suitable for mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] 1 is a schematic cross-sectional view of a substrate coated with a first photoresist layer in one embodiment of the present invention;

[0032] FIG2 is a schematic cross-sectional view of the structure of the substrate after photolithography and development in the embodiment shown in FIG1 ;

[0033] FIG3 is a schematic cross-sectional view of the structure of the substrate after hot-melt treatment in the embodiment shown in FIG1 ;

[0034] FIG4 is a schematic cross-sectional view of the structure of the protective layer deposited on the substrate in the embodiment shown in FIG1 ;

[0035] FIG5 is a schematic cross-sectional view of the structure of a metal layer deposited on a substrate in the embodiment shown in FIG1 ;

[0036] 6 is a schematic cross-sectional view of the structure of the substrate coated with a second photoresist layer in the embodiment shown in FIG1 ;

[0037] FIG7 is a schematic cross-sectional view of the structure of the substrate after secondary photolithography and development in the embodiment shown in FIG1 ;

[0038] 8 is a schematic cross-sectional view of the structure of the substrate after removing part of the metal layer and the second photoresist layer in the embodiment shown in FIG1 ;

[0039] FIG9 is a schematic cross-sectional view of the structure of the substrate after etching in the embodiment shown in FIG1 ;

[0040] FIG10 is a schematic structural diagram of a microlens structure according to an embodiment of the present invention;

[0041] FIG11 is a top view of a microlens structure in another embodiment of the present invention;

[0042] FIG12 is a test diagram of a sample passing a mapping test in Example 1 of the present invention;

[0043] FIG13 is a test chart showing that the sample in Comparative Example 1 of the present invention passed the mapping test.

[0044] Description of reference numerals:

[0045] 100, substrate; 110, first photoresist layer; 111, photoresist spherical structure; 112, photoresist column; 120, protective layer; 130, metal layer; 140, second photoresist layer; 141, window; 150, step structure; 160, microlens; 200, base. DETAILED DESCRIPTION

[0046] The specific embodiments of the present invention are described in detail below with reference to the accompanying drawings, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments.

[0047] Unless expressly stated otherwise, throughout the specification and claims, the term "comprise" or variations such as "include" or "comprising", etc., will be understood to include the stated elements or components but not to exclude other elements or other components.

[0048] The technical solution, its implementation process and principles will be further explained below with reference to the accompanying drawings.

[0049] Referring to Figures 1 to 9, a method for preparing a microlens includes the following steps:

[0050] S1. Forming a first photoresist layer 110 having a predetermined pattern structure in a first area on a surface of a substrate.

[0051] In this step, as shown in Figures 1 and 2 , a spherical microlens structure is designated as the pattern structure. A substrate 100 of appropriate size is selected, ensuring that its thickness is greater than the height of the microlenses 160 being fabricated. Substrate 100 is pretreated to remove contaminants such as particles, organic matter, process residues, and water vapor from its surface. A first photoresist layer 110 is then coated on the upper surface of substrate 100.

[0052] There are two methods for applying the photoresist: spin coating and spray coating. In this embodiment, spin coating, a conventional standard process, was used. Substrate 100 was placed on a chuck on a coating table. A vacuum was then applied, and approximately 15 ml of photoresist was dripped onto the center of substrate 100. The chuck was then rotated at a constant speed of 3500 rpm for 35 seconds to evenly coat the surface of substrate 100. Substrate 100 was then removed and heated on a 100°C hot plate for 90 seconds.

[0053] Among them, the bubbles in the photoresist need to be allowed to escape by standing still before use. When taking the photoresist with a dropper, the action should be gentle to avoid bringing in bubbles. The thickness of the coated first photoresist layer 110 is calculated and determined based on the height of the designed glue ball, and the general thickness range is adjusted between 15μm-30μm.

[0054] Afterwards, the substrate 100 coated with the first photoresist layer 110 can be pre-baked as needed to remove the solvent in the photoresist, enhance adhesion, release stress in the photoresist film, and prevent the photoresist from contaminating the equipment. In this embodiment, a hot plate pre-baking method is used. The hot plate pre-baking method uses a transmitted hot plate to heat the substrate 100 coated with the glue. The photoresist is heated outward from the contact surface between the substrate 100 and the photoresist, and is heated relatively evenly. The general pre-baking temperature is 85°C-120°C, and the time is 30s-90s.

[0055] The substrate 100 coated with the first photoresist layer 110 is then subjected to photolithography. In this embodiment, the photolithography is a conventional standard operation. Positive photoresist is usually used to make the gumballs. When exposed to ultraviolet light with a wavelength of about 365 nm, the photosensitive agent in the photoresist exposed to the ultraviolet light is decomposed, while the photoresist in the area not exposed to the ultraviolet light remains unchanged.

[0056] The exposed substrate 100 is then developed. The development process in this embodiment is also a standard procedure. Positive photoresist typically uses 3038 developer. The photoetched wafer is placed in the 3038 developer and shaken evenly for 20 seconds. The photoresist in the exposed areas dissolves, while the photoresist in the unexposed areas remains unchanged, ultimately leaving cylindrical photoresist columns 112. The photoresist columns 112 are then heat-melted to form smooth curved surfaces on their outer surfaces, thereby forming photoresist spherical structures 111.

[0057] As shown in FIG3 , the substrate 100 and the photoresist column 112 are subjected to a heat-melt treatment. In this embodiment, the heat-melt treatment is an existing processing technology. The photoresist column 112 is placed upside down in a vacuum environment and can be subjected to a heat-melt reflow treatment in an oven. A supporting device is provided in the oven so that the supporting device supports the photoresist column 112. The supporting device can be a tripod or other structure. The supporting portion of the tripod contacts and supports the substrate 100 around the photoresist column 112, thereby reducing damage to the photoresist column 112. The temperature of the oven is first raised to 40°C-60°C, and then raised to 120°C-140°C and maintained for 12-20 minutes. The photoresist column 112 is converted into a molten state under the high temperature state. Under the action of its own gravity, its outer surface is easy to form a smooth curved surface, thereby obtaining a photoresist spherical structure.

[0058] Among them, it is more appropriate to control the temperature range of the vacuum environment at 40°C-60°C (the substrate 100 is placed in the vacuum oven at room temperature, and the initial temperature is set to a relatively low temperature so that the two temperatures can be synchronized more quickly after being placed in the oven). After the temperature is raised to the set temperature (120°C-140°C, not exceeding 140°C), it is maintained for 12 minutes to 20 minutes.

[0059] In S2 , as shown in FIG. 4 , a protective layer 120 is formed on the surface of the substrate 100 , and the protective layer 120 overlaps the first photoresist layer 110 to form a protective structure.

[0060] In order to better support and protect the microlens 160 , the photoresist spherical structure 111 obtained in step S1 needs to undergo a secondary photolithography process on the substrate 100 to form a supporting structure surrounding the microlens 160 .

[0061] Since the material used to form the photoresist spherical structures in step S1 is photoresist, the formed photoresist spherical structures 111 are easily damaged during the secondary photolithography process on the substrate 100, thereby affecting the subsequent preparation of the microlenses 160. Therefore, it is necessary to deposit a protective layer 120 on the surface of the substrate 100. The protective layer 120 covers the surface of the photoresist spherical structures 111 formed in step S1 to form a protective structure for protecting the photoresist spherical structures 111 from photolithographic damage during the secondary photolithography process.

[0062] In this embodiment, the existing deposition technology can be used. In the deposition process of this embodiment, the coating temperature is set at 150°C-170°C, the coating rate is set at 4A / S-8A / S, the background vacuum is set at 5E-4Pa, APC: 2.5E-2pa, and the oxygen filling amount: 30sccm-40sccm.

[0063] Furthermore, protective layer 120 is made of silicon nitride, silicon oxide, or a combination thereof. This material protects the lens's topography and appearance during subsequent metal layer fabrication, ensuring lens consistency and improving product yield. The thickness of protective layer 120 is 100-200 nm.

[0064] In S3 , as shown in FIG. 8 , a metal layer 130 is formed on the third region of the surface of the substrate 100 , the second region of the surface of the substrate 100 is exposed, the second region surrounds the first region, and the third region surrounds the second region.

[0065] In this step, a support structure needs to be formed on the substrate 100. In this embodiment, the support structure is a step structure 150. In existing step fabrication processes, photoresist is generally used as a mask. However, photoresist has poor etching conformality, making it difficult to achieve vertical sidewalls of the step during etching, which can easily reduce the support effect for the microlens 160 and affect the subsequent packaging process. Therefore, a metal mask can be used. A uniform metal layer 130 is deposited on the end surface of the substrate 100. During the deposition of the metal layer 130, the metal layer 130 evenly covers the protective layer 120.

[0066] The material of the metal layer 130 includes one or more of Al, Zn, Mo, W, and Ta, and the thickness of the deposited metal layer 130 may be 0.5 μm-5 μm.

[0067] In addition, when depositing the metal, either electron beam evaporation or sputtering can be used to deposit the metal layer 130. The electron beam evaporation process uses one or more energy sources to convert into thermal energy under vacuum conditions, heating the metal plating material, causing it to evaporate or sublime, becoming gaseous particles (atoms, molecules, or atomic clusters) with a certain energy (0.1-0.3 eV). These gaseous particles leave the plating material surface and are transported to the surfaces of the substrate 100 and the protective layer 120 in a substantially collision-free, straight-line flight. Upon reaching the surfaces of the substrate 100 and the protective layer 120, the gaseous particles condense, nucleate, and grow into a solid-phase metal film, thereby completing the deposition of the metal layer 130.

[0068] When using the electron beam evaporation process, the evaporation rate can be set to 0.1nm / s-0.2nm / s, the electron beam power can be set to 150W-200W, the cavity temperature can be set to 30℃-40℃, and the umbrella frame rotation rate can be set to 10rpm-12rpm.

[0069] The sputtering process uses gas discharge to generate gas ionization. The positive ions, under the action of the electric field, bombard the cathode target at high speed, knocking out atoms or molecules from the cathode target. These atoms or molecules fly to the surface of the substrate being plated and deposit as a thin film. When using the sputtering process, the DC radio frequency can be set to 200W-250W, the temperature to 20℃-35℃, the Ar flow rate to 30sccm-50sccm, and the sputtering film formation rate to 0.1nm / s-0.2nm / s.

[0070] Wherein, in step S3, as shown in Figures 5, 6, and 7, the following steps are included:

[0071] S31, forming a second photoresist layer 140 on the first area and the second area of ​​the surface of the substrate 100, wherein the second photoresist layer 140 covers a portion of the protective layer 120 and the first photoresist layer 110;

[0072] S32, forming a metal layer 130 on the surface of the substrate 100, with a portion of the metal layer 130 covering the second photoresist layer 140;

[0073] S33 , removing the second photoresist layer 140 , and removing a portion of the metal layer 140 covering the second photoresist layer 140 , so that the metal layer 140 is only formed on the third region of the surface of the substrate 100 .

[0074] In this embodiment, a second photoresist layer 140 is coated on the surface of the substrate 100 after the protective layer 120 is deposited in step S2. The second photoresist layer 140 is formed by the same process as the first photoresist layer 110 formed in step S1. The second photoresist layer 140 coated on the base layer 100 is then subjected to a photolithography process and a development process. The coating process, photolithography process, and development process are the same as those in step S1 to remove the second photoresist layer 140 covering the third area on the surface of the substrate 100. Then, the metal layer 130 is deposited on the surface of the substrate 100.

[0075] In the third area, since there is no second photoresist layer 140, the metal layer 130 is directly deposited on the protective layer 120. In the first area and the second area, the metal layer 130 is deposited on the second photoresist layer 140. Thereafter, the second photoresist layer 140 is removed to remove the metal layer 130 on the first area and the second area, leaving only the metal layer 130 on the third area, thereby forming a metal mask.

[0076] The metal layer 130 on the third area surrounds the first area and the second area, so that the first area and the second area form a window. The window 141 can be a rectangular groove or a cylindrical groove, and the bottom length of the groove is greater than the diameter of the bottom plane of the photoresist spherical structure 111, so that the photoresist spherical structure 111 can be exposed in the window 141.

[0077] Furthermore, when removing the second photoresist layer 140 coated on the substrate 100, two methods are generally used: wet and dry. The wet method utilizes an organic solvent or a solution that is corrosive to the photoresist to dissolve or etch it away, thereby achieving the desired effect. The choice of a stripping solution must be non-reactive with or damage the substrate 100. Dry stripping utilizes oxygen plasma to ash the photoresist, achieving the desired effect.

[0078] For example, in this embodiment, wet stripping is used, and the substrate is placed in an NMP solution, the temperature is set to 80-90 degrees Celsius, and soaked for 5 minutes to 15 minutes to remove the second photoresist layer. Since the protective layer protects the photoresist spherical structure 111, it can effectively prevent the dissolution of the photoresist spherical structure 111.

[0079] In S4 , the substrate 100 with the protective structure and the metal layer 130 on its surface is simultaneously etched until a designated pattern structure is formed in a first area of ​​the surface of the substrate 100 and a groove structure is formed in a second area of ​​the surface of the substrate 100 .

[0080] An etching selectivity is determined based on the etching rates of the metal layer 130, the protective layer 120, and the substrate 100. The substrate 100 and the photoresist spherical structure 111 are etched to replicate the photoresist spherical structure 111 onto the substrate 100 to form a microlens 160. The substrate 100 with the metal layer 130 removed from around the photoresist spherical structure 111 is etched to form a groove-like structure, and a step structure 150 is formed with the substrate 100 with the remaining metal layer 130. The sidewalls of the step structure 150 are perpendicular to the bottom wall, and the height of the sidewalls of the step structure 150 is higher than the height of the microlens.

[0081] In this step, as shown in FIG9 , the thicknesses of the deposited metal layer 130 and protective layer 120, as well as the etching rates of the metal layer 130, protective layer 120, photoresist, and substrate 100 are measured respectively. Furthermore, the height from bottom to top of the microlens product having a spherical structure formed in step 2 is measured to calculate the corresponding etching selectivity, where the etching selectivity is calculated as substrate etching rate / metal etching rate.

[0082] In this embodiment, the etching selection ratio is 1: (10-20). During etching, plasma dry etching is selected.

[0083] Among them, in this embodiment, ICP is set to 400W-1000W, RF is set to 100W-500W, pressure is set to 2mtorr-10mtorr, gas selection is SF6, CH4, C4F8, CHF3 and one or more, flow range is 10sccm-50sccm.

[0084] Then, the dry etching recipe is adjusted according to the calculated etching selectivity, so that during etching, the protective layer 120 on the surface of the photoresist spherical structure 111 and the substrate 100 without the metal layer 130 mask are etched first. After the protective layer 120 is etched, the photoresist spherical structure 111 is etched until it is completely etched, thereby transferring the photoresist spherical structure to the substrate 100.

[0085] Since the etching rate of the metal layer 130 is relatively slow, the etching process is completed after the metal layer 130 is completely etched away. A groove-shaped step structure 150 and a micro lens 160 are etched on the substrate 100 . The micro lens 160 is located at the bottom of the step structure 150 .

[0086] Since the metal layer 130 is used as a mask when etching the step, the etching conformality is better, and the vertical sidewall of the step structure 150 can be better etched.

[0087] In addition, the calculated etching selectivity ensures that after etching is completed, the sidewalls of the step structure 150 extend vertically upward, and the extension height is greater than the height of the microlens 160, thereby better supporting and protecting the microlens 160. The vertical sidewalls of the step structure 150 also facilitate the subsequent packaging process of the microlens 160.

[0088] In the existing process for fabricating microlenses 160, a mask for the stepped structure 150 must first be prepared, followed by the photoresist spherical structure 111. Therefore, when fabricating the photoresist spherical structure, a window 141 is already formed on the substrate 100. Photoresist is then applied to the window 141, allowing a portion of the photoresist to fall through the opening of the window 141 to the bottom of the window 141. This portion of the photoresist is then subjected to photolithography, development, and heat-melting processes.

[0089] However, in this method, when coating the photoresist on the window 141, uneven coating is likely to occur, resulting in different heights of the glue columns formed subsequently, reducing the uniformity of the lens, and thus greatly affecting the yield of the product, which is very likely to cause waste of resources and increase production costs.

[0090] Through the above-mentioned concept, the present invention first prepares a photoresist spherical structure on a substrate 100, then deposits a protective layer 120 on the outer surface of the microlens product, and then prepares a stepped structure 150 to support the microlens 160. This effectively avoids the uneven photoresist coating problem during the preparation of the microlens product in the existing process, improves the uniformity of the prepared microlenses 160, and further improves the product yield.

[0091] The protective layer 120 is provided to protect the photoresist spherical structure 111 to prevent it from being damaged in subsequent processes.

[0092] In addition, by using a metal mask and etching the metal layer 130, the protective layer 120 and the photoresist at different rates, a support structure with vertical sidewalls is etched to improve the support and protection of the microlens 160. The support structure with vertical sidewalls can also facilitate subsequent packaging and mounting processes.

[0093] Referring to Figures 10 and 11 , a microlens 160 structure is fabricated using the aforementioned microlens fabrication method. The microlens 160 structure comprises a substrate 200, a stepped structure 150, and microlenses 160. Step structure 150 is a groove-like structure formed on substrate 200. Microlenses 160 are a predetermined pattern structure located on the bottom wall of step structure 150. The sidewalls of step structure 150 are perpendicular to the bottom wall, and the sidewalls of step structure 150 are higher than the height of microlenses 160.

[0094] In one embodiment of the present invention, the substrate 200 is made of silicon or quartz. A step structure 150 is formed by a vertical downward depression on one end surface of the substrate 200. The microlens 160 is formed at the bottom of the step structure 150. The material of the microlens 160 is the same as that of the substrate 200, namely silicon or quartz. The sidewalls of the step structure 150 are perpendicular to the bottom wall, and the height of the sidewalls is greater than the height of the microlens 160. Therefore, the step structure 150 can support and protect the microlens 160. Its vertical sidewalls also facilitate the subsequent packaging process of the microlens 160.

[0095] In one embodiment, the step structure 150 is a circular groove-shaped structure, and the diameter of the step structure 150 is larger than the diameter of the plane of the microlens 160. The microlens 160 and the step structure 150 are coaxially arranged, and the diameter of the bottom plane of the microlens 160 is smaller than the diameter of the step structure 150. This allows a certain gap between the sidewalls of the microlens 160 and the step structure 150, further facilitating the packaging process of the microlens 160.

[0096] In another embodiment, as shown in FIG. 11 , a plurality of step structures 150 and a plurality of microlenses 160 corresponding to the number of the step structures 150 are provided on the substrate 200 , and the plurality of step structures 150 are regularly distributed on the substrate 200 .

[0097] Among them, a plurality of step structures 150 can be distributed in a regular pattern or regular shape on the substrate 200 as needed, and a microlens 160 is formed in each step structure 150, so that the microlenses 160 can be prepared and controlled in large quantities, thereby improving production efficiency.

[0098] The technical solution of the present invention is further described in detail below in conjunction with several preferred embodiments and the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. The test methods in the following examples where specific conditions are not specified are generally based on conventional conditions. Example 1

[0099] In this embodiment, a microlens with a ROC (radius of curvature) of 1500, a sag of 30.3 μm, and a diameter of 600 μm is manufactured.

[0100] An 8-inch wafer is selected as the substrate, and a first photoresist layer 110 is coated on the surface of the wafer by a coating process. The thickness of the first photoresist layer 110 is 15 μm. Photoresist columns 112 are formed on the first area of ​​the wafer by a photolithography process and a development process. The photoresist columns 111 are then formed into photoresist spherical structures 112 by baking. The sagitta of the photoresist spherical structure 112 is increased by hot melting. The diameter of the photoresist spherical structure 112 is 600 μm and the sagitta is 30.3 μm.

[0101] Silicon nitride was deposited on the wafer to form a protective layer 120. The deposition temperature was set at 160°C, the deposition rate was set at 6 A / S, the background vacuum was set at 5E-4 Pa, the APC was set at 2.5E-2 Pa, and the oxygen injection rate was set at 35 sccm. The protective layer 120 covered the photoresist spherical structures 112. The thickness of the deposited protective layer 120 was 100 nm.

[0102] A second photoresist layer 140 is coated on the wafer with the protective layer 120 deposited thereon by a coating process. The thickness of the second photoresist layer 140 is 35 μm. A photoresist layer structure exposing the third region is formed by a photolithography process and a development process.

[0103] Then, Zn is deposited on the surface of the wafer and the second photoresist layer 140 by electron beam evaporation process. The thickness of the metal layer 130 is 2.5 μm. The evaporation rate is set to 0.2 nm / s, the electron beam power is 180 W, the chamber temperature is set to 35°C, and the umbrella frame rotation rate is 12 rpm.

[0104] The wafer is then placed in an NMP solution at 85 degrees Celsius for 12 minutes to remove the second photoresist layer 140 , thereby removing the metal layer 130 covering the second photoresist layer 140 , leaving only the metal layer 130 in the third area of ​​the wafer.

[0105] The wafer was then subjected to plasma dry etching with the following parameters: ICP at 600W, RF at 400W, pressure at 6mtorr, CH4 gas at a flow rate of 30sccm, and an etching selectivity of 1:20. The photoresist spherical structure 112 was etched and replicated onto the first region of the wafer. Using the metal layer 130 as a mask, a stepped structure 150 was etched onto the second region of the wafer. The resulting microlenses 160 had a diameter of 600μm and a height of 50μm, with a stepped structure height of 40μm. After fabrication, the sample was removed. Example 2

[0106] In this embodiment, a microlens with a ROC (radius of curvature) of 3000, a sag of 20.5 μm, and a diameter of 700 μm is manufactured.

[0107] An 8-inch wafer is selected as the substrate, and a first photoresist layer 110 is coated on the surface of the wafer through a coating process. The thickness of the first photoresist layer 110 is 10.3 μm. Photoresist columns 111 are formed on the first area of ​​the wafer through a photolithography process and a development process. The photoresist columns 111 are then baked to form a photoresist spherical structure 112. The diameter of the photoresist spherical structure 112 is 700 μm and the arrow height is 20.5 μm.

[0108] Silicon nitride is deposited on the wafer to form a protective layer 120 , and the thickness of the deposited protective layer 120 is 150 nm. The deposition method and parameters are consistent with those in Example 1.

[0109] A second photoresist layer 140 is coated on the wafer with the protective layer 120 deposited thereon by a coating process. The thickness of the second photoresist layer 140 is 23 μm. A photoresist layer structure exposing the third region is formed by a photolithography process and a development process.

[0110] Then, Zn is deposited on the surface of the wafer and the second photoresist layer 140 by electron beam evaporation process. The thickness of the metal layer 130 is 2.5 μm. The electron beam evaporation process parameters are consistent with those in Example 1.

[0111] The wafer is then placed in an NMP solution at 85 degrees Celsius for 12 minutes to remove the second photoresist layer 140 , thereby removing the metal layer 130 covering the second photoresist layer 140 , leaving only the metal layer 130 in the third area of ​​the wafer.

[0112] The wafer was then subjected to plasma dry etching, using the same parameters as in Example 1. The photoresist spherical structure 112 was etched and replicated onto the first region of the wafer. Using the metal layer 130 as a mask, a stepped structure 150 was etched onto the second region of the wafer. The resulting microlenses 160 had a diameter of 700 μm, a height of 20.5 μm, and a stepped structure height of 30 μm. After preparation, the sample was removed. Example 3

[0113] In this embodiment, a microlens with a ROC (radius of curvature) of 700, a sag of 46.2 μm, and a diameter of 500 μm is manufactured.

[0114] An 8-inch wafer is selected as the substrate, and a first photoresist layer 110 is coated on the surface of the wafer by a coating process. The thickness of the first photoresist layer 110 is 23.3 μm. Photoresist columns 111 are formed on the first area of ​​the wafer by a photolithography process and a development process. The photoresist columns 111 are then baked to form photoresist spherical structures 112. The diameter of the photoresist spherical structure 112 is 500 μm and the arrow height is 46.2 μm.

[0115] Silicon nitride is deposited on the wafer to form a protective layer 120 , and the thickness of the deposited protective layer 120 is 200 nm. The deposition method and parameters are consistent with those in Example 1.

[0116] A second photoresist layer 140 is coated on the wafer with the protective layer 120 deposited thereon by a coating process. The thickness of the second photoresist layer 140 is 50 μm. A photoresist layer structure exposing the third region is formed by a photolithography process and a development process.

[0117] Then, Zn is deposited on the surface of the wafer and the second photoresist layer 140 by electron beam evaporation process. The thickness of the metal layer 130 is 2.5 μm. The electron beam evaporation process parameters are consistent with those in Example 1.

[0118] The wafer is then placed in an NMP solution at 85 degrees Celsius for 12 minutes to remove the second photoresist layer 140 , thereby removing the metal layer 130 covering the second photoresist layer 140 , leaving only the metal layer 130 in the third area of ​​the wafer.

[0119] The wafer was then subjected to plasma dry etching, using the same parameters as in Example 1. The photoresist spherical structure 112 was etched and replicated onto the first region of the wafer. Using the metal layer 130 as a mask, a stepped structure 150 was etched onto the second region of the wafer. The resulting microlenses 160 had a diameter of 500 μm and a height of 46.2 μm, with a stepped structure height of 60 μm. After preparation, the sample was removed.

[0120] Comparative Example 1

[0121] In this comparative example, a conventional microlens preparation method is used to prepare a microlens with a ROC (radius of curvature) of 1500, a sag of 30.3 μm, and a diameter of 600 μm. The specific steps include:

[0122] An 8-inch wafer is used as the substrate, and then a 5-μm-thick photoresist is coated on the etched side of the wafer as a mask. The photoresist is exposed and developed using a photolithography process and a development process. The developed wafer is then plasma dry-etched to form a step structure with a height of 50 μm on the second area of ​​the wafer.

[0123] The etched wafer is then subjected to a second photoresist coating with a thickness of 20 μm. A photoresist column is formed at the bottom of the step structure of the wafer through photolithography and development processes, and then the photoresist column is made into a photoresist spherical structure by baking. The diameter of the photoresist spherical structure is 600 μm and the arrow height is 30.3 μm.

[0124] The baked wafer is subjected to secondary plasma dry etching to etch and copy the photoresist spherical structure onto the wafer. The diameter of the prepared microlens is 600 μm, the height is 30.3 μm, and the step height is 50 μm. After preparation, the sample is taken out.

[0125] Using the samples of Example 1 and Comparative Example 1 as examples, mapping tests were performed to examine the microlens surface shape, curvature, profile, and laser co-focusing of the samples. As shown in Figures 12 and 13, the gray area A represents a qualified area, and the dark gray area B represents a failed area. Compared with the microlenses prepared in Comparative Example 1, the uniformity of the microlenses prepared in Example 1 was improved from 10% to within 3%, and the yield was increased from 60% to over 90%.

[0126] It should be understood that the above embodiments are merely illustrative of the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent variations or modifications made in accordance with the spirit and substance of the present invention are intended to be encompassed within the scope of protection of the present invention.

[0127] The foregoing descriptions of specific exemplary embodiments of the present invention are for purposes of illustration and description. These descriptions are not intended to limit the invention to the precise forms disclosed, and it is apparent that many variations and modifications are possible in light of the foregoing teachings. The exemplary embodiments have been selected and described for the purpose of explaining the specific principles of the invention and their practical application, thereby enabling those skilled in the art to realize and utilize a variety of exemplary embodiments of the invention and various options and modifications. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A method for preparing a microlens, characterized in that: The following steps are involved: S1, forming a first photoresist layer having a specified pattern structure in a first area on the surface of the substrate; S2, forming a protective layer on the surface of the substrate, wherein the protective layer is superimposed on the first photoresist layer to form a protective structure; S3, forming a metal layer on the third area of ​​the surface of the substrate, with the second area of ​​the surface of the substrate being exposed, the second area surrounding the first area, and the third area surrounding the second area; S4. Simultaneously etching the substrate whose surface is covered with the protection structure and the metal layer until the designated graphic structure is formed in a first area on the surface of the substrate and a groove structure is formed in a second area on the surface of the substrate.

2. A method for preparing a microlens according to claim 1, characterized in that: The material of the protective layer includes silicon nitride, silicon oxide or a combination thereof.

3. The method for preparing a microlens according to claim 1, wherein: The thickness of the protective layer is 100nm-200nm.

4. The method for preparing a microlens according to claim 1, wherein: The step S3 comprises: S31, forming a second photoresist layer on the first area and the second area of ​​the surface of the substrate, wherein the second photoresist layer partially covers the protective layer and the first photoresist layer; S32, forming the metal layer on the surface of the substrate, wherein a portion of the metal layer covers the second photoresist layer; S32 , removing the second photoresist layer, and removing a portion of the metal layer covering the second photoresist layer, so that the metal layer is only formed on the third area of ​​the surface of the substrate.

5. A method for preparing a microlens according to claim 4, characterized in that: The material of the metal layer includes one or more of Al, Zn, Mo, W, and Ta.

6. The method for preparing a microlens according to claim 4, wherein: The thickness of the metal layer is 0.5 μm-5 μm.

7. A method for preparing a microlens according to claim 5 or 6, characterized in that: The metal layer is deposited by any of electron beam evaporation and sputtering processes.

8. The method for preparing a microlens according to claim 1, wherein: The substrate and the photoresist spherical structure are etched by a plasma dry method.

9. The method for preparing a microlens according to claim 1, wherein: The etching selection ratio is 1:(10-20).

10. A microlens structure, characterized in that: The microlens is prepared by the microlens preparation method according to any one of claims 1 to 9.

11. The microlens structure according to claim 10, characterized in that: include: A substrate, a step structure and a microlens, wherein the step structure is a groove-shaped structure formed on the substrate, the microlens is the specified pattern structure and is located on the bottom wall of the step structure, the sidewall and bottom wall of the step structure are perpendicular, and the sidewall height of the step structure is higher than the height of the microlens.

12. The microlens structure according to claim 10, characterized in that: include: A substrate, a step structure and a micro lens, wherein the step structure is a circular groove structure, and the diameter of the step structure is larger than the diameter of the plane of the micro lens.

13. The microlens structure according to claim 11 or 12, characterized in that: The substrate is provided with a plurality of step structures and a plurality of micro lenses corresponding to the number of the step structures, and the plurality of step structures are regularly distributed on the substrate.

14. The microlens structure according to claim 11 or 12, characterized in that: The substrate and the microlens are made of silicon or quartz.

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