A photolithography-polishing direct molding manufacturing method for SU-8 microlens array

Abstract

The present invention relates to a photolithography-polishing direct molding manufacturing method for a SU-8 microlens array, comprising: arranging a photoresist SU-8 on a substrate, and then molding it into a SU-8 microcolumn array through a photolithography process; and polishing the SU-8 microcolumn array using a chemical mechanical polishing technique to mold it into a SU-8 microlens array. The method is suitable for directly in-situ integrated manufacturing of a microlens array on a molded device without the need for additional alignment, transfer, and bonding steps. The prepared SU-8 microlens array has the advantages of good morphology, controllable size, good chemical stability, good thermal stability, and the like.

Description

Technical Field

[0001] The invention relates to the field of micro-nano manufacturing technology, and in particular to a photolithography-polishing direct molding manufacturing method for a SU-8 microlens array. Background Art

[0002] Microlenses are one of the common micro-optical elements in the field of optics, usually referring to miniature lenses with sizes ranging from a few microns to a few millimeters. An array formed by microlenses distributed in a certain way is called a microlens array. As an important micro-optical element, microlens arrays have been widely studied and applied in the fields of display, sensing, lighting, photovoltaics, etc. due to their excellent performance such as large field of view, large depth of field, small size, and high integration.

[0003] Microlenses can be integrated and manufactured on light-emitting devices (such as vertical cavity surface emitting lasers) through some preparation methods, such as droplet injection method, thermal reflow method, heated embossing method, etc. The droplet injection method refers to the use of a micro syringe to spray ultraviolet-cured polymer droplets onto a substrate. This method is difficult to control the shape of the droplets, so the size and surface shape of the microlens array are difficult to control. The thermal reflow method mainly relies on photolithography and thermal reflow technology to form a spherical structure of the photoresist. The prepared photoresist sphere can be left on the aperture window of the top-emitting device as a microlens, or it can be used as an etching mask to form a microlens on the back of the bottom-emitting device through plasma etching. Although this method is a simple microlens manufacturing method, the contact angle of the microlens is only affected by the wettability of the photoresist on the substrate and the ambient air, so it is difficult to control. In the heated embossing method, the microlens is formed by pressing a mold onto a polymer substrate at high temperature. The polymer substrate is usually polymethyl methacrylate as a material for the microlens. The heated embossing method does not require the use of any microlens-shaped mold, avoiding surface defects caused by contact between the mold wall and the polymer. However, the microlenses made by the heated embossing method and some indirect methods cannot be easily integrated on device chips or wafers, requiring additional optical alignment, transfer and other steps. Therefore, a method is needed to integrate and manufacture microlenses with high precision positioning in situ on the surface of a molded device. Summary of the invention

[0004] The task of the present invention is to provide a SU-8 microlens array photolithography-polishing direct molding manufacturing method, which can in-situ manufacture high-precision positioned SU-8 microlenses on the surface of a molded device, and the prepared microlens array has the advantages of good morphology, controllable size, good chemical stability and thermal stability.

[0005] In view of the problems existing in the prior art, the present invention provides a photolithography-polishing direct molding manufacturing method of a SU-8 microlens array, comprising:

[0006] Arranging photoresist SU-8 on the substrate, and then forming it into a SU-8 microcolumn array through photolithography technology, including spinning, baking, exposure, and development processes; and

[0007] The SU-8 micro-pillar array is polished by chemical mechanical polishing technology to form a SU-8 micro-lens array.

[0008] In one embodiment of the present invention, the step of arranging photoresist SU-8 on the substrate further includes arranging an adhesion promoter on the substrate, and the substrate includes a formed device, and the device includes a photoelectric device or a detection device.

[0009] In one embodiment of the present invention, the process further includes fine polishing the SU-8 microlens array.

[0010] In one embodiment of the present invention, the step of arranging photoresist SU-8 on the substrate comprises:

[0011] The photoresist SU-8, model SU-8 3050, was spin-coated on the substrate with the adhesion promoter. The spin-coating parameters included spinning at a rotation speed of 500 rpm (low speed) for 10 seconds and then spinning at a rotation speed of 1200 rpm (high speed) for 30 seconds.

[0012] In one embodiment of the present invention, when the height of the SU-8 microcolumn array is less than or equal to 100 μm, the model of the photoresist SU-8 used to prepare the microcolumn array is SU-8 3050; and

[0013] When the height of the SU-8 microcolumn array is between 100 μm and 650 μm, the type of the selected photoresist SU-8 is SU-8 3050, SU-8 2100 or SU-8 2150.

[0014] In one embodiment of the present invention, forming the SU-8 microcolumn array by photolithography comprises:

[0015] Placing the substrate on a hot plate for pre-baking to obtain a photoresist film;

[0016] Exposing the photoresist film under a photolithography machine;

[0017] Placing the substrate on a hot plate for intermediate baking;

[0018] placing the substrate in a developer for development; and

[0019] The substrate is placed on a hot plate for post-baking to obtain a cured SU-8 microcolumn array.

[0020] In one embodiment of the present invention, during pre-baking, the temperature is raised to 95° C. by program control and heated for 20 minutes to obtain a photoresist film with a film thickness of 100 μm; and / or

[0021] Exposure parameters include: exposure power density is 9mJ / cm 2 , exposure time 10s; and / or

[0022] During the intermediate baking, the temperature is raised to 95°C and heated for 5 minutes; and / or

[0023] The developer is propylene glycol methyl ether acetate, and the developing time is 3 to 5 minutes; and / or

[0024] The height of the SU-8 microcolumn array is 100 μm.

[0025] In one embodiment of the present invention, when polishing the SU-8 microcolumn array, a flexible polishing pad and an alumina polishing liquid are selected, and the selected polishing disk speed range is 5-70 rpm; and

[0026] When polishing the SU-8 micro-pillar array, the precision polishing fixture is adjusted so that the SU-8 micro-pillar array is completely embedded in the nap of the velvet polishing pad.

[0027] In one embodiment of the present invention, the flexible polishing pad is a velvet polishing pad, the cross-sectional diameter of the velvet is 20-30 μm, and the height is about 1 mm; and / or

[0028] The particle size of the aluminum oxide polishing liquid is 1 μm.

[0029] In one embodiment of the present invention, the SU-8 microlens array is finely polished using a silica sol polishing liquid with a particle size of 20 nm.

[0030] In one embodiment of the present invention, the adhesion promoter includes OmniCoat or HMDS; and

[0031] The operations of disposing the adhesion promoter on the substrate include spin coating the reagent and hot plate baking.

[0032] In one embodiment of the present invention, the step of arranging a tackifier on the substrate comprises:

[0033] 3-4 mL of OmniCoat solution was dropped on the substrate, and the spin coating parameters were 500 rpm (low speed) for 10 s, followed by 3000 rpm (high speed) for 30 s. The substrate was then placed on a 200 °C hot plate and heated for 1 min, and then cooled to room temperature along the hot plate.

[0034] The present invention has at least the following beneficial effects: the present invention discloses a photolithography-polishing direct molding manufacturing method for a SU-8 microlens array, which is based on mature photolithography technology and chemical mechanical polishing technology, and can prepare a large-area SU-8 microlens array with good morphology, high controllability, good chemical stability and good thermal stability; the method has the advantages of simplicity, low cost, good repeatability, high yield, etc.; the method is an integrated manufacturing method for a microlens array, and since both SU-8 photolithography and chemical mechanical polishing technology are compatible with integrated circuit semiconductor processes, the method is suitable for directly integrating and manufacturing the microlens array in situ on a formed device without the need for additional alignment, transfer, and bonding steps, and has a wide range of popularization and application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to further illustrate the above and other advantages and features of various embodiments of the present invention, a more specific description of various embodiments of the present invention will be presented with reference to the accompanying drawings. It will be understood that these drawings only depict typical embodiments of the present invention and are therefore not to be considered as limiting the scope thereof. In the accompanying drawings, for clarity, identical or corresponding parts will be represented by identical or similar reference numerals.

[0036] Figure 1 The flowchart of a photolithography-polishing direct molding manufacturing method of a SU-8 microlens array according to an embodiment of the present invention is shown.

[0037] Figure 2 A schematic diagram of a SU-8 micropillar array according to an embodiment of the present invention is shown.

[0038] Figure 3 FIG. 4 is a schematic diagram showing a SU-8 microlens array according to an embodiment of the present invention.

[0039] Figure 4 A scanning electron microscope image of a velvet polishing pad according to one embodiment of the present invention is shown.

[0040] Figure 5 and Figure 6 A scanning electron microscope image of a SU-8 microlens array according to one embodiment of the present invention is shown. DETAILED DESCRIPTION

[0041] It should be noted that various components in the various drawings may be shown exaggeratedly for illustrative purposes and are not necessarily correct to scale.

[0042] In the present invention, each embodiment is only intended to illustrate the aspects of the present invention and should not be construed as limiting.

[0043] In the present invention, unless otherwise specified, the quantifiers "a", "an" and "an" do not exclude the presence of a plurality of elements.

[0044] It should also be pointed out that in the embodiments of the present invention, for the sake of clarity and simplicity, only a portion of the parts or components may be shown, but a person of ordinary skill in the art will understand that under the teachings of the present invention, required parts or components may be added as needed in specific scenarios.

[0045] It should also be pointed out that within the scope of the present invention, the terms "same", "equal", "equal to" and the like do not mean that the two values ​​are absolutely equal, but allow a certain reasonable error, that is, the terms also cover "substantially the same", "substantially equal", and "substantially equal to".

[0046] It should also be pointed out that in the description of the present invention, the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions 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 explicitly or implicitly indicating 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 explicitly or implicitly indicating relative importance.

[0047] In addition, the embodiments of the present invention describe the process steps in a specific order, but this is only for the convenience of distinguishing the steps, and does not limit the sequence of the steps. In different embodiments of the present invention, the sequence of the steps can be adjusted according to the adjustment of the process.

[0048] As an important light source, vertical cavity surface emitting lasers have been widely studied and applied in the fields of fiber-optic communication, optical interconnection, lidar, printing, etc. In terms of scalability and uniformity, vertical cavity surface emitting laser arrays have more advantages than edge emitting laser arrays. Vertical cavity surface emitting lasers are usually used in combination with microlenses to improve beam collimation or focusing.

[0049] The embodiment of the present invention provides a method for manufacturing a lens with high-precision positioning directly on the surface of a device, including spin coating SU-8 photoresist on the device, then forming a SU-8 micro-column array through a photolithography process; and polishing the SU-8 micro-column array to form a SU-8 micro-lens array. Compared with the conventional micro-lens manufacturing method, the method has the advantages of simplicity, low cost, good repeatability, high yield, etc., and is suitable for directly integrating the micro-lens array in situ on the formed device, and has a wide range of promotion and application value.

[0050] Figure 1The flowchart of a photolithography-polishing direct molding manufacturing method of a SU-8 microlens array according to an embodiment of the present invention is shown. Figure 2 A schematic diagram of a SU-8 micropillar array according to an embodiment of the present invention is shown. Figure 3 FIG. 4 is a schematic diagram showing a SU-8 microlens array according to an embodiment of the present invention. Figure 4 A scanning electron microscope image of a velvet polishing pad according to one embodiment of the present invention is shown. Figure 5 and Figure 6 A scanning electron microscope image of a SU-8 microlens array according to one embodiment of the present invention is shown.

[0051] like Figure 1 As shown, a photolithography-polishing direct molding manufacturing method of a SU-8 microlens array comprises the following steps:

[0052] Step 1: providing a substrate 1 , and optionally arranging an adhesion promoter on the substrate 1 .

[0053] Provide a clean glass substrate 1, and optionally arrange a tackifier on the substrate 1 to increase the bonding force. The tackifier may be, for example, OmniCoat or HMDS. The tackification operation includes spin coating reagents, hot plate baking, and the like. Specifically, drop 3-4 mL of OmniCoat solution on the substrate 1, rotate at 500 rpm (low speed) for 10 seconds, and then rotate at 3000 rpm (high speed) for 30 seconds. Then place the substrate 1 on a 200°C hot plate and heat for 1 minute, and cool to room temperature with the hot plate. In other embodiments of the present invention, a tackifier may not be arranged on the substrate.

[0054] Step 2, arranging photoresist SU-8 on substrate 1, and then forming it into SU-8 micro-pillar array 2 through photolithography process. SU-8 micro-pillar array includes multiple SU-8 micro-pillars. The photolithography process may include processes such as spinning, baking, exposure, and development.

[0055] Glue baking includes pre-baking, mid-baking and post-baking.

[0056] Spinning: Spin-coat the substrate 1 with the tackifier with photoresist SU-8, model SU-8 3050, and the spin-coating parameters include spinning at a speed of 500 rpm (low speed) for 10 seconds, and then spinning at a speed of 1200 rpm (high speed) for 30 seconds; Pre-baking: Place the substrate 1 on a hot plate, program-controlled temperature rise to 95°C, and heat for 20 minutes to obtain a photoresist film with a film thickness of about 100 μm; Exposure: Expose the photoresist film under a photolithography machine, and the exposure parameters are: exposure power density is 9 mJ / cm 2, exposure time 10s; mid-bake, placing substrate 1 on a hot plate, program-controlled heating to 95°C, heating for 5min; developing, placing substrate 1 in a developer for development, the developer is propylene glycol methyl ether acetate (PGMEA), and the developing time is 3min to 5min; post-bake, placing substrate 1 on a hot plate for program-controlled heating to obtain a fully cured SU-8 microcolumn array 2, the height of the SU-8 microcolumn array 2 is about 100μm, such as Figure 2 shown.

[0057] The height and width of the SU-8 microcolumn array 2 are controllable and are regulated by the photoresist and patterning parameters. For example, when the height of the SU-8 microcolumn array 2 is less than or equal to 100 μm, the type of photoresist SU-8 used to prepare the microcolumn array can be SU-8 3050, but is not limited thereto; when the height of the SU-8 microcolumn array 2 is between 100 μm and 650 μm, the type of photoresist SU-8 used can be SU-8 2100, SU-8 2150, etc., but is not limited thereto. The arrangement of the SU-8 microcolumn array 2 can be circular arrangement, rectangular arrangement, hexagonal arrangement, etc.

[0058] Those skilled in the art should understand that the photoresist types and specific processing parameters selected in the above embodiments are merely illustrative and not restrictive, and therefore the process parameters may be adjusted and / or other types of photoresists may be selected according to actual needs.

[0059] Step 3: using chemical mechanical polishing technology, polishing the SU-8 micro-pillar array 2 to form a SU-8 micro-lens array.

[0060] In some embodiments of the present invention, a flexible polishing pad is selected and an aluminum oxide polishing liquid with a particle size of 1 μm is selected. Figure 4 As shown, the flexible polishing pad is a velvet polishing pad, and the diameter of its hair is 20-30μm and the height is about 1mm. By adjusting the precision polishing fixture, ensure that the SU-8 micro-pillar array is completely embedded in the hair of the velvet polishing pad, ensure a certain embedding depth, and ensure that the SU-8 micro-pillar array can fully contact the hair during the polishing process, which is a key step in the formation of the microlens array. Adjust the speed of the polishing disk to a suitable value for polishing. Use the Logitech PM5 precision grinding and polishing machine to perform chemical mechanical polishing on the SU-8 micro-pillar array.

[0061] The size of the polishing abrasive used for polishing directly affects the surface roughness of the microlens after lens formation. The selected polishing disc speed range is 5-70rpm. The polishing disc speed is positively correlated with the material removal rate and negatively correlated with the microlens forming time. However, too fast a polishing disc speed may cause the SU-8 microcolumn to break, affecting the final microlens yield, so it is necessary to select a reasonable polishing speed.

[0062] Those skilled in the art should understand that, in the embodiments of the present invention, the abrasive component in the polishing liquid used for polishing includes but is not limited to aluminum oxide, and the particle size of the polishing liquid includes but is not limited to 1 μm.

[0063] like Figure 3 As shown, Ⅰ represents the height of the upper plano-convex lens, Ⅱ represents the height of the lower base, and Ⅲ represents the total height of the microlens structure. Compared with the size of the SU-8 microcolumn, the size change caused by polishing is very small, so the diameter and height of the prepared SU-8 microcolumn can represent the size of the target SU-8 microlens.

[0064] In one embodiment of the present invention, the SU-8 microlens array can be finely polished to further reduce its surface roughness. The scanning electron microscope image of the final SU-8 microlens array is as follows: Figure 5 and Figure 6 shown.

[0065] In some embodiments of the present invention, a silica sol polishing liquid with a particle size of 20 nm can be selected to perform fine polishing on the SU-8 microlens array to further reduce its surface roughness and make the lens surface smoother. Those skilled in the art should understand that in the embodiments of the present invention, the polishing liquid used for fine polishing includes but is not limited to silicon dioxide, and the particle size of the polishing liquid includes but is not limited to 20 nm.

[0066] The smaller the abrasive particle size of the silica sol polishing liquid used for fine polishing, the better the effect of fine polishing. The time of fine polishing is determined by the size of the microlens and the size of the abrasive particle.

[0067] If the formed SU-8 microlens is polished for a long time using silica sol polishing liquid, the surface shape of the microlens will be changed to a certain extent. Therefore, it is necessary to reasonably control the fine polishing time to obtain a microlens with good morphology and smooth surface.

[0068] It should be noted that the method of the present invention is not limited to SU-8 and velvet polishing pads. Any material that meets the characteristics described in the specification can be used as a microlens material, and any flexible polishing pad that meets the characteristics described in the specification can be used as a polishing pad for the method of the present invention. Various details related to the microlens material, polishing pad, etc. can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0069] The above-mentioned SU-8 microlens array photolithography-polishing direct molding manufacturing method is based on mature photolithography technology and chemical mechanical polishing technology, and can prepare a large-area SU-8 microlens array with good morphology, high controllability, good chemical stability and thermal stability, and the method has the advantages of simplicity, low cost, good repeatability, and high yield. This method is an integrated manufacturing method for microlens arrays. Since both SU-8 photolithography and chemical mechanical polishing technology are compatible with integrated circuit semiconductor processes, this method is suitable for directly integrating microlens arrays in situ on formed devices without the need for additional alignment, transfer, and bonding steps, and has a wide range of promotion and application value. The formed devices may include but are not limited to optoelectronic devices or detection devices.

[0070] The SU-8 microlens array produced by the above method can be used in vertical cavity surface emitting lasers. The SU-8 microlens array can be directly integrated and manufactured in situ on the surface of the formed vertical cavity surface emitting laser through this method. The traditional method usually requires optical alignment, transfer, bonding and other steps after the lens is made. In addition, the present invention can also accurately control the diameter and height of the microlens by adjusting the lithography parameters, which is conducive to the integrated integration of micro-optical elements and vertical cavity surface emitting lasers. Vertical cavity surface emitting lasers with integrated SU-8 microlenses can be used in laser radar, printing, three-dimensional sensing and other fields.

[0071] Although some embodiments of the present invention have been described in this application document, it will be appreciated by those skilled in the art that these embodiments are merely shown as examples. Those skilled in the art may conceive of numerous variations, alternatives, and improvements under the teachings of the present invention without departing from the scope of the present invention. The appended claims are intended to define the scope of the present invention and to cover methods and structures within the scope of these claims themselves and their equivalents.

Claims

1. A SU-8 microlens array photolithography-polishing direct molding manufacturing method, characterized in that: include: Arranging photoresist SU-8 on the substrate, and then forming it into a SU-8 micro-column array through a photolithography process; The SU-8 micro-pillar array is polished by chemical mechanical polishing technology to form a SU-8 micro-lens array, wherein the SU-8 micro-lens array includes a plurality of SU-8 micro-lenses, and the SU-8 micro-lenses include a lower base and an upper plano-convex lens located on the lower base; When polishing the SU-8 micropillar array, a flexible polishing pad and alumina polishing liquid are used, and the polishing disk speed range is 5-70rpm; The flexible polishing pad is a velvet polishing pad, the cross-sectional diameter of the velvet is 20-30 μm, and the height is about 1 mm; When polishing the SU-8 micro-pillar array, the precision polishing fixture is adjusted so that the SU-8 micro-pillar array is completely embedded in the nap of the velvet polishing pad; and Fine polishing of SU-8 microlens array.

2. The photolithography-polishing direct molding manufacturing method of the SU-8 microlens array according to claim 1 is characterized in that: Before the step of arranging the photoresist SU-8 on the substrate, the step further includes arranging an adhesion promoter on the substrate; and / or The photolithography process includes baking, exposure and developing processes; and / or The substrate includes a formed device, and the device includes an optoelectronic device or a detection device.

3. The photolithography-polishing direct molding manufacturing method of the SU-8 microlens array according to claim 1 is characterized in that: The SU-8 microlens array was finely polished using a silica sol polishing liquid with a particle size of 20 nm.

4. The photolithography-polishing direct molding manufacturing method of the SU-8 microlens array according to claim 2 is characterized in that: The step of arranging photoresist SU-8 on the substrate comprises: The photoresist SU-8, model SU-83050, was spin-coated on the substrate with the adhesion promoter. The spin-coating parameters included spinning at a rotation speed of 500 rpm for 10 seconds and then spinning at a rotation speed of 1200 rpm for 30 seconds.

5. The photolithography-polishing direct molding manufacturing method of the SU-8 microlens array according to claim 2, characterized in that: When the height of the SU-8 microcolumn array is less than or equal to 100 μm, the model of the photoresist SU-8 selected for preparing the microcolumn array is SU-8 3050; and When the height of the SU-8 microcolumn array is between 100 μm and 650 μm, the type of the selected photoresist SU-8 is SU-8 3050, SU-8 2100 or SU-8 2150.

6. The photolithography-polishing direct molding manufacturing method of the SU-8 microlens array according to claim 2, characterized in that: The forming of the SU-8 microcolumn array by photolithography process comprises: Placing the substrate on a hot plate for pre-baking to obtain a photoresist film; Exposing the photoresist film under a photolithography machine; Placing the substrate on a hot plate for intermediate baking; placing the substrate in a developer for development; and The substrate is placed on a hot plate for post-baking to obtain a cured SU-8 microcolumn array.

7. The photolithography-polishing direct molding manufacturing method of the SU-8 microlens array according to claim 6 is characterized in that: During pre-baking, the temperature is raised to 95° C. by program control and heated for 20 minutes to obtain a photoresist film with a film thickness of 100 μm; and / or Exposure parameters include: exposure power density is 9mJ / cm 2 , exposure time 10s; and / or During the intermediate baking, the temperature is raised to 95°C and heated for 5 minutes; and / or The developer is propylene glycol methyl ether acetate, and the developing time is 3 to 5 minutes; and / or The height of the SU-8 microcolumn array is 100 μm.

8. The photolithography-polishing direct molding manufacturing method of the SU-8 microlens array according to claim 1, characterized in that: The particle size of the aluminum oxide polishing liquid is 1 μm.

9. The photolithography-polishing direct molding manufacturing method of the SU-8 microlens array according to claim 2, characterized in that: The adhesion promoter comprises OmniCoat or HMDS, and the operation of disposing the adhesion promoter on the substrate comprises spin coating the reagent and hot plate baking, The step of arranging the adhesion promoter on the substrate comprises the following steps: 3-4 mL of OmniCoat solution was dropped on the substrate, and the spin coating parameters were 500 rpm for 10 s, followed by 3000 rpm for 30 s. The substrate was then placed on a hot plate at 200 °C for 1 min and cooled to room temperature as the hot plate was cooled.

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