Preparation method for arrayed cascaded microlens group, arrayed exposure apparatus, and application of arrayed cascaded microlens group

Abstract

Disclosed in the present application are a preparation method for an arrayed cascaded microlens group, an arrayed exposure apparatus, and the application of an arrayed cascaded microlens group. The preparation method comprises: applying a photoresist layer to a surface of a substrate; performing first underexposure in a first region, and performing second underexposure in a second region, wherein the first region and the second region have an overlapping portion but do not completely overlap, and the overlapping portion generates superimposed underexposure to form regional graded underexposure; performing development to form a regional photoresist pillar array; and transforming photoresist pillars into curved surfaces, and using the curved surfaces to perform patterned etching on the substrate to obtain an arrayed cascaded microlens group. The present application uses underexposure technology combined with regional superimposed exposure to directly perform regional exposure with different doses, ultimately preparing a wafer-level arrayed cascaded microlens group, and thus has the significant advantages of low cost, convenient operation, high preparation efficiency and high yield, and can be widely applied in the manufacturing processes of various imaging sensors, display devices and photovoltaic devices.

Description

Preparation method of arrayed cascade microlens group, arrayed exposure device and application

[0001] This application claims priority to Chinese invention patent application number CN202410247795.X, filing date March 5, 2024, entitled “Preparation method of arrayed cascaded microlens group, arrayed exposure device and application”, which is incorporated herein by reference in its entirety. Technical Field

[0002] The present application relates to the field of micro-nano processing technology for optical devices, and in particular to a method for preparing an arrayed cascade microlens group, an arrayed exposure device, and applications thereof. Background Art

[0003] With the continued advancement of Moore's Law, optical and semiconductor devices are facing higher demands for integration, precision, and stability. At the same time, microlenses have become an indispensable component in fields such as optical communications and photovoltaics. The primary function of microlenses is to shape light beams (such as homogenization, collimation, and aberration correction). However, to achieve these functions, multiple lenses are often combined (for example, the microlens laser homogenization method offered by Thorlabs, which consists of two plano-convex lenses and a microlens array). This method places extremely stringent requirements on device integration and precision, seriously affecting device applications. Furthermore, high-end M×N arrays of cascaded microlenses are difficult to manufacture and have low yield rates.

[0004] Specifically, some existing technologies use a laser direct writing process to produce a single or multi-layer columnar photoresist array on a substrate. By varying the exposure dose, the height and morphology of the columnar photoresist in the array are arranged in a certain pattern. The columnar photoresist array is then reflowed into a microlens through a heating and cooling process. However, the laser direct writing process has high equipment and process costs, and the process is complex, resulting in a low yield, which is not conducive to the widespread application of array-type cascaded microlens groups.

[0005] Other existing technologies use a metasurface mask close to the photoresist surface, use linearly polarized light in the ultraviolet band to enter the metasurface mask, and expose the corresponding photoresist area below the metasurface mask; move the metasurface mask to expose other areas of the photoresist until the exposure is completed on the required areas of the photoresist; then develop the substrate coated with the photoresist, and form a microlens array structure on the exposed photoresist after development. However, this implementation method can only use a smaller metasurface mask to prepare microlenses of the same size in each area, and cannot obtain a regionalized array with microlenses of different sizes in different areas. It is also difficult to apply it in some fields with more complex optical path characteristics.

[0006] Summary of the Invention

[0007] In response to the shortcomings of the existing technology, the purpose of this application is to provide a method for preparing an arrayed cascaded microlens group, an arrayed exposure device and its application. The purpose is to provide a convenient, efficient, low-cost and high-yield method for preparing an arrayed cascaded microlens group to meet the wide application needs in the high-end optical field, specifically for use in high-end precision application fields such as optical communication lenses and infrared temperature measurement lenses.

[0008] To achieve the aforementioned invention objectives, the technical solutions adopted in this application include:

[0009] In a first aspect, the present application provides a method for preparing an array-type cascaded microlens group, comprising:

[0010] A photoresist layer is first applied to the surface of a substrate, wherein the photoresist layer has a plurality of groups of areas to be exposed distributed along a first direction, each group of areas to be exposed including a first area, a second area, and a third area distributed along the first direction, wherein the first area overlaps and does not overlap with the second area, and the third area is the overlapping area of ​​the first area and the second area, and the first direction is parallel to the substrate surface;

[0011] Then, performing a first underexposure and a second underexposure on the first region and the second region respectively, so as to generate superimposed underexposure in the third region, thereby forming regionalized graded underexposure in the photoresist layer;

[0012] Then developing the photoresist layer to form a regionalized resin column array;

[0013] Then, the glue pillars in the regionalized glue pillar array are transformed into arcuate bodies, and the substrate is pattern-etched using the arcuate bodies to obtain an array-type cascade microlens group.

[0014] Based on the above technical solution, the present application does not adopt a complex and expensive laser direct writing process, nor does it use a small and difficult-to-change metasurface mask to prepare the microlens array. Instead, it combines underexposure with regionalized multiple superimposed exposure. By setting a lower single exposure amount, the number of exposures in different areas is controlled to achieve separate adjustment of the total exposure dose in different areas, thereby achieving precise and controllable regionalized exposure at a lower cost and higher efficiency, and ultimately obtaining an array-type cascaded microlens group with a regionalized change trend.

[0015] Furthermore, regarding how to transform the gel column, the preparation method specifically includes the following steps:

[0016] The regionalized glue column array is annealed to make the glue columns fluid, and the glue columns are transformed into the arcuate bodies by utilizing the surface tension.

[0017] The aforementioned implementation of regionalized graded underexposure and annealing conversion can produce satisfactory microlens array products in some situations with lower requirements. However, the inventors of this application have also discovered that for some applications with higher optical property requirements, such as high-end optical instruments, the requirements for lens surface roughness are extremely high, and it is difficult to meet these requirements using only the aforementioned overall implementation scheme.

[0018] This is because during the R&D implementation process, it was discovered that multiple overlapping underexposures caused the photoresist to undergo multiple and multi-depth curing processes. The internal curing was not absolutely uniform, and multiple different curing zones were often formed. There were certain boundaries between these curing zones, similar to the grain boundaries of crystals. During the annealing conversion process, although a certain degree of fluidity was generated, the differences between the different curing zones could not be completely eliminated, which brought about the problem of surface roughness. This is different from the rule in the art that the glue columns formed by full exposure usually have a smooth surface after annealing and flowing into balls. Furthermore, this uneven surface will cause the shape of the etched structure to be uneven during the process of etching and patterning and transferring it to the substrate, making it difficult to meet the precision requirements of high-end applications.

[0019] Therefore, in order to solve the above problems and achieve wide application in higher-end fields, the preparation method further specifically includes:

[0020] The said glue column is first formed into a cambered front surface after the said annealing treatment;

[0021] Simultaneously or subsequently, the arcuate front surface is smoothed to obtain the arcuate body.

[0022] Furthermore, the smoothing process specifically includes the following steps:

[0023] The arcuate front body is brought into contact with a smoothing liquid so as to generate a solvation effect on a portion of the material on the surface of the arcuate front body, thereby performing the smoothing treatment.

[0024] Furthermore, the smoothing liquid is selected from high-boiling-point organic matter or organic solvent, specifically including any one of tetramethylammonium hydroxide and propylene glycol monomethyl ether acetate or a combination of two thereof; the temperature of the smoothing treatment is 130-240° C., and the time is 1-9 minutes.

[0025] The above technical solution smoothes the curved front surface after annealing and converting it into a ball, so that its surface is converted into a smoother surface; the preferred smoothing treatment method is to perform a solvation reaction through a smoothing liquid, so that the surface undergoes a certain degree of dissolution and leveling, thereby achieving smoothing and obtaining a smooth surface.

[0026] The specific principle and process should be: using high-temperature heat treatment to cure the photoresist. Typically, in the chip manufacturing process, photoresist is first coated on the chip surface, then exposed and developed using a photolithography machine, and finally cured by thermal reflow. During the thermal reflow process, the chemical substances in the photoresist react to form solid polymers, thereby forming a microstructure. After the high-temperature annealing treatment, when exposed to a higher temperature solvent, some rough surface areas that have not been fully cured can still undergo solvation with the solvent, resulting in a certain degree of surface fluidity. Through the dual effects of temperature and solvent, the surface self-levels, thereby obtaining a smooth curved surface.

[0027] In addition, there are more ways to achieve surface smoothness. A consistent smoothing effect can also be achieved by improving the composition of the photoresist layer.

[0028] Specifically, the photoresist layer is further doped with a leveler, and the leveler is used to enable the glue column to spontaneously form a smooth surface during the annealing process.

[0029] Furthermore, the leveler includes any one or a combination of two or more of sulfate, polyorganosiloxane, and silicate; and in the photoresist layer, the mass fraction of the leveler is 0.1-2%.

[0030] Another preferred embodiment of the present application is to incorporate a leveler into the photoresist layer. During the high-temperature annealing process, the leveler will spontaneously migrate to the surface of the photoresist layer, producing a certain degree of dissolution and leveling effect on the surface photoresist, thereby obtaining a smooth surface.

[0031] Of course, the specific surface smoothing method is not limited to one of the above two methods. The above two methods can also be implemented together to achieve the ultimate smoothing effect. In addition, other surface treatment methods, such as surface plasma etching and polishing, can theoretically also achieve the same surface smoothing effect.

[0032] The above technical solution is about a specific method for forming a curved surface, and further about how to perform the above regionalized underexposure. When performing the first underexposure and the second underexposure, a movable mask is used to perform regional division.

[0033] More specifically, further, the movable mask includes a first light-shielding body and a second light-shielding body, and the preparation method specifically includes:

[0034] adjusting the distance between the first light shielding body and the second light shielding body to perform the first underexposure corresponding to the first area;

[0035] moving the first light shielding body and / or the second light shielding body to reduce the distance between them, and performing the second underexposure corresponding to the second area;

[0036] Alternatively, adjusting the distance between the first light shielding body and the second light shielding body to perform the second underexposure corresponding to the second area;

[0037] The first light shielding body and / or the second light shielding body are moved to enlarge the distance therebetween, and the first underexposure is performed corresponding to the first area.

[0038] As shown in the preferred embodiment of the present application, another technical contribution provided by the present application is the development of an efficient, inexpensive and precisely controllable regionalized graded underexposure technology, which uses a light-shielding body that can be adjusted in real time, such as a light-blocking plate, and forms light-shielding areas corresponding to different first areas and second areas by adjusting the spacing of the light-shielding body between multiple exposures during underexposure, thereby providing a convenient and fast technical solution that can be adjusted during the exposure process.

[0039] Of course, feasible implementation methods are not limited to this. If multiple different photolithography masks are used and replaced between multiple underexposure processes, the same function can be achieved. However, this implementation method is complicated and time-consuming, and is prone to operational errors, resulting in preparation failure.

[0040] As for how to realize dot matrix exposure of multiple glue columns, further, the first underexposure and the second underexposure are both exposed by dot matrix light generated by the same array mask.

[0041] Regarding underexposure parameters, the exposure doses of the first and second underexposures are 30-70% of the full exposure of the photoresist layer. However, it should be noted that although the exposure dose (e.g., the product of a single continuous light intensity and the continuous light duration) is 30-70% of the full exposure, this does not mean that the degree of photoinduced crosslinking of the photoresist is also equal to the exposure dose percentage. For example, in a single round of exposure, the exposure dose is 50%, but the curing ratio (cured photoresist mass in the exposed area / total photoresist mass) caused by this exposure round is far less than 50%.

[0042] Moreover, the above exposure ratios are only a common range of ratio selections and are not limited to the above ratios. If the process requirements are different, for example, if there are many levels of cascade lenses, the exposure amount of a single exposure may be reduced to achieve multi-level adjustment.

[0043] In order to realize the above-mentioned preparation method, especially the key technical means of regional array underexposure, the second aspect of the present application also provides an arrayed exposure device for preparing an arrayed cascade microlens group, which includes a dot matrix light-emitting unit, a movable shading unit and a carrying unit; the dot matrix light-emitting unit is used to provide dot matrix light; the movable shading unit is used to cooperate with the dot matrix light-emitting unit so that the dot matrix light has an adjustable regional size; the carrying unit is used to carry a substrate having a photoresist layer so that the photoresist layer receives underexposure of the dot matrix light with an adjustable regional size.

[0044] Furthermore, the movable light-shielding unit includes a first light-shielding body and a second light-shielding body with adjustable spacing, and a driving structure for driving the first light-shielding body and / or the second light-shielding body to move.

[0045] Furthermore, the dot matrix light emitting unit includes a light source and an array mask; along the light propagation direction, the movable light shielding unit is arranged between the light source and the array mask, or behind the array mask.

[0046] On the third aspect, the present application also provides applications of the arrayed cascade microlens group prepared by the above-mentioned preparation method in the fields of imaging sensing, display, and photovoltaic devices.

[0047] Based on the above technical solution, compared with the existing technology, the beneficial effects of this application include:

[0048] The method for preparing an arrayed cascaded microlens group provided in this application derives the size arrangement of the cascaded microlens group through calculation and optical fitting, and directly performs regionalized exposure with different doses using underexposure technology combined with regionalized superposition exposure. This method then develops a glue column array of varying heights. Subsequently, through forming techniques such as thermal reflow annealing, an arrayed cascaded microlens group with varying curvature radii can be fabricated at the wafer level. This method offers significant advantages such as low cost, ease of operation, high preparation efficiency, and high yield, and can be widely applied in the manufacturing processes of various imaging sensors, displays, and photovoltaic devices.

[0049] The above description is only an overview of the technical solution of the present application. In order to enable those skilled in the art to more clearly understand the technical means of the present application and implement them in accordance with the contents of the specification, the following is an explanation of the preferred embodiment of the present application with detailed drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] FIG1 is a schematic flow chart of a preparation method provided in a typical embodiment of the present application;

[0051] FIG2 is a schematic structural diagram of a movable mask in a preparation method provided in a typical embodiment of the present application;

[0052] FIG3 is a schematic structural diagram of an array-type cascaded microlens group provided in a typical embodiment of the present application;

[0053] FIG4 is a schematic structural diagram of another array-type cascaded microlens group provided in a typical embodiment of the present application;

[0054] FIG5 is a surface roughness test diagram of a single microlens in an array-type cascaded microlens group before surface smoothing provided in a typical embodiment of the present application;

[0055] FIG6 is a surface roughness test diagram of a single microlens in an array-type cascaded microlens group after surface smoothing provided in a typical embodiment of the present application. DETAILED DESCRIPTION

[0056] In view of the shortcomings of the existing technology, the inventors of this case, after long-term research and extensive practice, have proposed the technical solution of this application. The following will further explain this technical solution, its implementation process and principles.

[0057] In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application may also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present application is not limited to the specific embodiments disclosed below.

[0058] Moreover, relational terms such as “first” and “second” are merely used to distinguish one component or method step from another with the same name, but do not necessarily require or imply any actual relationship or order between these components or method steps.

[0059] As shown in FIG1 , an embodiment of the present application provides a method for preparing an array-type cascaded microlens group, which includes the following steps:

[0060] 1. Cover the substrate surface with a photoresist layer.

[0061] 2. Perform a first underexposure in a first area on the surface of the photoresist layer, and perform a second underexposure in a second area on the surface of the photoresist layer, wherein the first area and the second area have an overlapping portion but do not completely overlap, so that the overlapping portion (the third area) produces a superimposed underexposure to form a regionalized graded underexposure in the photoresist layer.

[0062] 3. Developing the photoresist layer that has undergone the regionalized graded underexposure to form a regionalized resist column array.

[0063] 4. Converting the glue pillars in the regionalized glue pillar array into arcuate bodies, and using the arcuate bodies to perform patterned etching on the substrate to obtain an array-type cascade microlens group.

[0064] Of course, not only one group of arrayed cascade microlens groups can be prepared on the substrate surface, but also multiple groups can be prepared. Corresponding to the area to be exposed, there can be one group or multiple groups, depending on the preparation requirements.

[0065] The first underexposure and the second underexposure do not refer to only two underexposures, but rather to the correlation between two underexposures in a plurality of underexposures set based on the specific number of levels and size changes of the array-type cascaded microlens group. For example, the size of the exposure window can be gradually reduced from the periphery to the center to perform multi-level underexposure, so that the later exposed area will receive more underexposures than the earlier exposed area. Of course, depending on different specific preparation requirements, it is not necessarily limited to the multiple underexposure method with the periphery gradually shrinking toward the center (it is understandable that in the exposure method of gradually shrinking from large to small, the third area is equivalent to the second area within the first area). Other equivalent alternative exposure rules are also acceptable. For example, a portion of the first area extends beyond the second area, and another portion overlaps with the second area. In this way, the overlapping portion receives a higher dose of exposure than the non-overlapping portion.

[0066] Details regarding the photoresist layer, substrate, exposure wavelength, etc. do not involve the main technical concept of this application. It is sufficient to refer to various existing microlens preparation technical solutions to select appropriate photoresist and substrate materials to meet its functional requirements.

[0067] Microlenses are commonly used in optical communications, optical sensing, AI and other fields. Currently on the market, the conventional method is to use a combination of multiple lenses to complete various functions, which seriously affects the integration and precision of the device, and the high-end M×N array-type cascaded microlens group is difficult to produce and has a low yield. Therefore, the purpose of this application is to provide a simple method: to obtain the arrangement of the cascaded microlens group through calculation and optical fitting, and to use underexposure technology to directly prepare M×N glue column arrays of different heights, and then to prepare M×N array-type cascaded microlens groups with different curvature radii at the wafer level through one-time molding using thermal reflow technology.

[0068] As some typical application examples of the above technical solution, the preparation method can be implemented using the following preparation process:

[0069] 1. According to the design requirements, a uniform layer of photoresist is coated on wafers of different sizes such as 4 / 6 / 8, and then a pre-bake process at a certain temperature (70-120°C) is performed to form the photoresist layer. Of course, how to form the photoresist layer in this step is only exemplary, and feasible photoresist layer formation methods are not limited to this. In this regard, please refer to many existing technical solutions.

[0070] 2. Design the original photolithography pattern according to the target, underexpose different glue pillars with different curvature radii (different exposure times and different exposure times). Use a customized movable light shielding frame installed on the photolithography machine (as an optional movable mask, its structure is shown in Figure 2 and can be customized according to the desired structure pattern) to superimpose underexposure on different areas. After a single development, an M×N glue pillar array of different heights is obtained.

[0071] 3. Finally, a thermal reflow annealing process was used to transform and prepare rubber balls with different curvature radii, and then the rubber balls were patterned and transferred to the substrate using etching technology to prepare an M×N array-type cascaded microlens group with different curvature radii.

[0072] Based on the different structures of the movable light shielding plate frame, different regional array lens groups can be formed. For example, as shown in Figure 3, by moving the light shielding plate toward the center in a one-dimensional direction, a lens distribution with a high center and low ends can be formed. As shown in Figure 4, by moving the light shielding plate in the two-dimensional directions of left and right and up and down, a rectangular ring-shaped stepped pattern can be formed. In addition, in a more preferred embodiment, a circular ring-shaped movable light shielding method such as a camera shutter can be used to form a circumferential ring-shaped stepped pattern. All feasible embodiments are achieved by customizing the movable mask based on the desired array shape, and are not limited to the specific shapes shown in the examples.

[0073] In addition, the movement of the light-shielding body is not limited to the movement from large to small. The movement from small to large and gradually expanding can also achieve the function of the middle area being exposed more times than the surrounding areas, and still obtain a glue column array with regionalized exposure and development.

[0074] The above-mentioned preparation method can produce an array of cascaded microlenses sufficient for general applications. However, due to the surface roughness issue mentioned above, whether directly using photoresist balls as lenses or using etching technology to transfer the pattern to the substrate to form lenses, it will be difficult to meet the requirements of higher-end applications. This was beyond the inventors' expectations at the beginning of the development.

[0075] Therefore, some more preferred implementation cases of the present application have added preferred technical means for surface smoothing, which include two implementation methods. One is to smooth the arc-shaped precursor with a certain surface roughness formed by annealing, such as using some solvents or etching reaction liquids to level the surface; the other is to optimize the material of the photoresist layer itself so that it spontaneously forms a smooth surface during high-temperature reflow annealing treatment.

[0076] A specific first treatment method is, for example, after annealing into balls, smoothing is performed by post-treatment, such as by contact with a high-temperature, high-boiling-point organic solvent to perform surface micro-leveling, but it is not limited to this. Other methods, such as surface etching and polishing, can also smooth the uneven micro-surface.

[0077] Another treatment method, for example, involves doping the photoresist with additives that have a leveling effect. These additives spontaneously form a smooth surface during the annealing process. Of course, the list of possible additives is not limited to the examples above. Any substance that is corrosive to the photoresist can be used as an additive and dissolved or dispersed in the photoresist to achieve a leveling effect.

[0078] The technical solution of the present application is further described in detail below through several embodiments and in conjunction with the accompanying drawings. However, the selected embodiments are only used to illustrate the present application and do not limit the scope of the present application.

[0079] Example 1

[0080] This embodiment illustrates the preparation of an M×N array-type cascaded microlens group with different curvature radii, as shown below:

[0081] First, a photoresist is spread on a 6-inch silicon wafer at a rotation speed of 4000 rpm, and the photoresist is baked and cured at 100° C. to form a photoresist layer.

[0082] Then, the customized movable plate holder is placed on the UV photolithography machine, and different areas are underexposed using different exposure times and different exposure times. The exposure process parameters (exposure dwell time, total exposure times, and single underexposure dose) are formulated based on the initial design and fine-tuned based on multiple repeated experiments. It only takes 2 minutes to complete the exposure.

[0083] Then, the preparation of rubber columns of different heights is completed through a single development time of developer, and the rubber columns are made to flow into balls through a heating reflux process to prepare rubber balls with different curvature radii.

[0084] Then, plasma etching technology is used to pattern the microlenses onto the substrate to prepare M×N array-type cascade microlens groups with different curvature radii.

[0085] The resulting array-type cascaded microlens group features a precise and orderly distribution of regionalized, multi-sized array lenses. Through multiple batches of trial production, its yield can reach approximately 80%, fluctuating depending on the precision requirements. In contrast, existing technical solutions rely solely on laser direct writing equipment and grayscale exposure equipment to prepare individual gel balls. This is not only expensive, but often takes several days or even more than ten days to achieve wafer-level structure preparation, resulting in a long cycle and impractical for mass production. Furthermore, this complex preparation process is extremely prone to various defects, making it difficult to accurately calculate the batch yield and completely unsuitable for large-scale application.

[0086] Example 2

[0087] This embodiment is substantially the same as embodiment 1, and is mainly a further improvement of the preparation method of embodiment 1, as shown below:

[0088] As shown in FIG5 , although the arrayed cascade microlens group prepared in Example 1 achieved technical effects such as high yield and high production efficiency, after magnifying and observing its surface height distribution, it can be found that its surface still has some unevenness, especially the glue balls corresponding to the glue pillars that have been repeatedly under-exposed and superimposed.

[0089] The improvement of this embodiment compared to embodiment 1 is that after the rubber balls are formed by the thermal reflow annealing treatment, the substrate containing the rubber balls is immersed in a smoothing liquid, which is heated and melted tetramethylammonium hydroxide, for 5 minutes at a treatment temperature of 170°C.

[0090] The substrate containing the rubber balls was taken out and the surface of the rubber balls was observed. As shown in FIG6 , it was found that the regional unevenness had basically disappeared and was replaced by a more uniform surface height distribution.

[0091] After the same etching process, the surface of the silicon microlens formed by transferring to the substrate surface also becomes smoother.

[0092] Example 3

[0093] This embodiment also illustrates the improvement of embodiment 1, which is as follows:

[0094] A certain amount of silicone oil (polymethylsiloxane) is added to the photoresist as a leveler, and the mass fraction of the leveler in the baked photoresist layer is 1%.

[0095] After the same multiple superimposed underexposures, one development, and thermal reflow annealing, the surface morphology of the formed rubber ball is similar to that shown in FIG6 . It can be seen that the surface naturally has a uniform height distribution. The silicon lens finally obtained after etching is also smoother than that in Example 1.

[0096] The implementation method provided in this embodiment further simplifies the implementation process and is more conducive to large-scale preparation.

[0097] Example 4

[0098] This embodiment is substantially the same as embodiment 2, with the main difference being that propylene glycol monomethyl ether acetate is used as the smoothing fluid, the treatment temperature is 140° C., and the treatment time is 9 minutes.

[0099] Similarly to Example 2, a relatively smooth high-end precision microlens group can be obtained.

[0100] Example 5

[0101] This embodiment is substantially the same as embodiment 3, with the main difference being that the leveling agent is replaced with sodium silicate in an amount of 2%.

[0102] Similarly to Example 3, a relatively smooth high-end precision microlens group can be obtained.

[0103] Based on the above-described implementation cases, it is clear that the method for preparing an arrayed cascaded microlens group provided in the embodiments of the present application derives the size arrangement of the cascaded microlens group through calculation and optical fitting, and directly performs regionalized exposure with different doses using underexposure technology combined with regionalized superposition exposure. Thus, after development, an array of glue pillars of different heights is prepared. Subsequently, through forming techniques such as thermal reflow annealing, an arrayed cascaded microlens group with different curvature radii can be prepared at the wafer level. This method has the significant advantages of low cost, easy operation, high preparation efficiency, and high yield, and can be widely used in the production processes of various imaging sensors, displays, and photovoltaic devices.

[0104] It should be understood that the above embodiments are merely illustrative of the technical concepts and features of this application. Their purpose is to enable those familiar with the art to understand the content of this application and implement it accordingly. They are not intended to limit the scope of protection of this application. Any equivalent changes or modifications made in accordance with the spirit and substance of this application shall be included within the scope of protection of this application.

Claims

1. A method for preparing an array-type cascaded microlens group, characterized in that: include: S1. A photoresist layer is first applied to a substrate surface. The photoresist layer has a plurality of groups of exposed regions distributed along a first direction. Each group of exposed regions includes a first region, a second region, and a third region distributed along the first direction. The first region overlaps and does not overlap with the second region. The third region is the overlapping region of the first and second regions. The first direction is parallel to the substrate surface. S2. Then, performing a first underexposure and a second underexposure on the first region and the second region, respectively, to generate a superimposed underexposure in the third region, thereby forming regionalized graded underexposure in the photoresist layer; a movable mask is used to divide the regions during the first underexposure and the second underexposure, wherein the movable mask includes a first light shielding body and a second light shielding body, specifically comprising: Adjusting the distance between the first light shielding body and the second light shielding body to perform the first underexposure corresponding to the first area; moving the first light shielding body and / or the second light shielding body to reduce the distance between them to perform the second underexposure corresponding to the second area; Alternatively, adjusting the distance between the first light shielding body and the second light shielding body to perform the second underexposure corresponding to the second area; moving the first light shielding body and / or the second light shielding body to increase the distance between them to perform the first underexposure corresponding to the first area; Wherein, the first underexposure and the second underexposure are both exposed by dot matrix light generated by the same array mask; S3. Thereafter, the photoresist layer is developed to form a regionalized glue column array; Then, the regionalized glue column array is annealed to make the glue columns fluid, and the glue columns are transformed into a curved front by using surface tension, and the curved front is smoothed simultaneously or subsequently to obtain a curved surface; The smoothing process specifically includes: The arcuate front is brought into contact with a smoothing liquid so that a portion of the material on the surface of the arcuate front produces a solvation effect, thereby achieving the smoothing process; and / or the photoresist layer is doped with a leveling agent, which is used to cause the photoresist column to spontaneously form a smooth surface during the annealing process, thereby achieving the smoothing process; S4. Using the arcuate body to perform patterned etching on the substrate to obtain an array-type cascaded microlens group.

2. The preparation method according to claim 1, characterized in that The smoothing fluid includes any one of tetramethylammonium hydroxide and propylene glycol monomethyl ether acetate or a combination of the two; The temperature of the smoothing treatment is 130-240° C., and the time is 1-9 minutes.

3. The preparation method according to claim 1, characterized in that The leveling agent includes any one or a combination of two or more of sulfate, polyorganosiloxane, and silicate; In the photoresist layer, the mass fraction of the leveler is 0.1-2%.

4. The preparation method according to claim 1, characterized in that The exposure doses of the first underexposure and the second underexposure are 30-70% of the full exposure of the photoresist layer.

5. Application of the arrayed cascade microlens assembly prepared by the preparation method according to any one of claims 1 to 4 in the fields of imaging sensing, display or photovoltaic devices.