Optical element with arc-shaped surface and method for processing same

Abstract

The application relates to the field of optical element processing, and discloses an optical element with an arc-shaped curved surface and a processing method thereof, which comprises the following steps: obtaining a pretreated substrate, the pretreated substrate comprising a substrate and a patterned photoresist on the surface of the substrate, the surface of the patterned photoresist away from the substrate being an arc-shaped curved surface; softening the patterned photoresist and bombarding the patterned photoresist with plasma to form a treated photoresist, the surface of the treated photoresist away from the substrate being an arc-shaped curved surface; and etching the substrate with the treated photoresist as a mask to form an arc-shaped curved surface on the surface of the substrate and obtain the optical element with the arc-shaped curved surface. The surface of the patterned photoresist is flattened by softening the patterned photoresist and bombarding the arc-shaped surface with plasma, the arc-shaped surface of the treated photoresist is transferred to the substrate by etching the substrate with the treated photoresist as a mask, and the roughness of the arc-shaped surface on the substrate is reduced.

Description

Technical Field

[0001] This application relates to the field of optical element processing, and in particular to an optical element with an arcuate surface and a processing method thereof. Background Technology

[0002] Optical elements with curved surfaces (such as microlenses or microlens arrays) are widely used in devices such as optocouplers, digital projectors, optical microscopes, and smartphone cameras. The roughness of the curved surface of the optical element has a significant impact on the performance of the optical element.

[0003] The fabrication method based on laser grayscale lithography and dry etching is a process capable of mass-producing optical components with highly uniform curved surfaces. It involves forming a patterned photoresist mask on a substrate, followed by etching to create the curved surface. However, the curved surfaces produced by this method currently exhibit relatively high roughness, around 5, which negatively impacts the performance of the optical components.

[0004] Therefore, how to reduce the roughness of curved surfaces on optical components is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] The purpose of this application is to provide an optical element with an arc-shaped surface and a method for processing the same, so as to reduce the roughness of the arc-shaped surface on the optical element.

[0006] To address the aforementioned technical problems, this application provides a method for fabricating an optical element with an arc-shaped curved surface, comprising:

[0007] A pre-processed substrate is obtained, the pre-processed substrate comprising a substrate and a patterned photoresist located on the surface of the substrate, wherein the surface of the patterned photoresist away from the substrate is an arc-shaped curved surface;

[0008] The patterned photoresist is softened and bombarded with plasma to form a treated photoresist, wherein the surface of the treated photoresist away from the substrate is an arc-shaped curved surface.

[0009] The substrate is etched using the processed photoresist as a mask to form an arc-shaped surface on the surface of the substrate, thereby obtaining an optical element with an arc-shaped surface.

[0010] Optionally, softening the patterned photoresist and bombarding the patterned photoresist with plasma includes:

[0011] The pretreated substrate is placed in the cavity of a plasma stripper, the cavity is heated to soften the patterned photoresist, and the surface of the patterned photoresist is bombarded by plasma.

[0012] Optionally, the temperature range for heating the cavity is 70℃~80℃.

[0013] Optionally, when bombarding the surface of the patterned photoresist with plasma, the power range of the plasma stripper is 200W to 500W, and the bombardment time ranges from 30s to 180s; and / or,

[0014] The gases used for bombardment include oxidizing gases and fluorine-based gases, with a volume ratio of fluorine-based gases to oxidizing gases ranging from 1:1 to 1:3.

[0015] Optionally, using the treated photoresist as a mask to etch the substrate to form an arcuate surface on the substrate includes:

[0016] The substrate is etched using the treated photoresist as a mask, and the curved surface morphology of the treated photoresist is copied to the surface of the substrate at a 1:1 ratio to form an arc-shaped surface on the surface of the substrate. The etching gas includes CHF3, inert gas, SF6 and O2, and the volume ratio of CHF3, inert gas, SF6 and O2 is in the range of (30-60):(30-60):(1-10):(10-30).

[0017] Optionally, obtaining the preprocessed substrate includes:

[0018] Photoresist is spin-coated onto the substrate;

[0019] The photoresist is pre-baked;

[0020] Laser direct writing exposure is performed on the photoresist after pre-baking;

[0021] Post-baking is performed on the exposed photoresist;

[0022] The post-baked photoresist is developed to form a patterned photoresist on the surface of the substrate.

[0023] Optionally, before spin-coating the photoresist onto the substrate, the method further includes:

[0024] Clean the substrate to remove dirt from its surface.

[0025] Optionally, pre-baking the photoresist includes:

[0026] The photoresist is heated to a first temperature.

[0027] The photoresist is further heated to a second temperature, which is higher than the first temperature.

[0028] Optionally, the first temperature is 65°C, and the heating time at the first temperature is 5 min to 15 min; the second temperature is 95°C, and the heating time at the second temperature is 5 min to 35 min.

[0029] This application also provides an optical element with an arcuate surface, which is obtained by any of the above-described processing methods for optical elements with arcuate surfaces.

[0030] This application provides a method for fabricating an optical element with an arcuate surface, comprising: obtaining a pre-processed substrate, the pre-processed substrate including a substrate and a patterned photoresist located on the surface of the substrate, wherein the surface of the patterned photoresist away from the substrate is an arcuate surface; softening the patterned photoresist and bombarding the patterned photoresist with plasma to form a post-processed photoresist, wherein the surface of the post-processed photoresist away from the substrate is an arcuate surface; and etching the substrate using the post-processed photoresist as a mask to form an arcuate surface on the surface of the substrate, thereby obtaining an optical element with an arcuate surface.

[0031] As can be seen, the processing method in this application obtains a pre-processed substrate including a substrate and a patterned photoresist. The surface of the patterned photoresist is an arc-shaped surface. The patterned photoresist is softened to make the arc-shaped surface of the patterned photoresist flatter. During the softening process, plasma is used to bombard the arc-shaped surface, which can further promote the flattening of the arc-shaped surface. That is, a processed photoresist with low roughness and a flatter surface can be obtained. Then, the processed photoresist is used as a mask to etch the substrate, transferring the arc-shaped surface shape of the processed photoresist to the substrate. This makes the roughness of the arc-shaped surface on the substrate relatively low, that is, an optical element with low surface roughness can be obtained.

[0032] In addition, this application also provides an optical element with an arcuate surface that has the above-mentioned advantages. Attached Figure Description

[0033] To more clearly illustrate the technical solutions of the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 A flowchart illustrating a method for fabricating an optical element with an arcuate surface, provided as an embodiment of this application;

[0035] Figure 2This is a process flow diagram of a method for fabricating an optical element with an arc-shaped surface, provided in an embodiment of this application. Detailed Implementation

[0036] To enable those skilled in the art to better understand the present application, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are merely some embodiments of the present application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0037] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0038] As described in the background section, current methods for fabricating optical components with curved surfaces involve forming a patterned photoresist mask on a substrate using photoresist, followed by etching the substrate to create the curved surface. However, the curved surfaces produced by this method currently have a relatively high roughness, around 5, which affects the performance of the optical components.

[0039] In view of this, this application provides a method for fabricating an optical element with an arc-shaped curved surface. Please refer to [the relevant documentation]. Figure 1 The method includes:

[0040] Step S101: Obtain a pre-processed substrate, the pre-processed substrate including a substrate and a patterned photoresist located on the surface of the substrate, the surface of the patterned photoresist away from the substrate being an arc-shaped curved surface.

[0041] The substrate can be made of other materials such as silicon wafers; no specific limitation is made in this embodiment.

[0042] It should be noted that this embodiment does not limit the method of obtaining the pretreated substrate, and the method can be chosen by the user. A pre-made pretreated substrate can be used directly, or a pretreated substrate can be made by the user.

[0043] Step S102: Soften the patterned photoresist and bombard the patterned photoresist with plasma to form a treated photoresist, wherein the surface of the treated photoresist away from the substrate is an arc-shaped curved surface.

[0044] During the softening process, patterned photoresist can make the curved surface of the photoresist flatter. At the same time, using plasma bombardment can further promote the planarization process of the photoresist.

[0045] It is important to emphasize that this step involves softening the photoresist, not reflowing it. The hardness of the softened photoresist is greater than that of the reflowed photoresist. When bombarded, it can not only promote planarization but also adjust the curvature angle of the curved surface.

[0046] It should be noted that this embodiment does not limit the methods of softening and bombarding the patterned photoresist. For example, softening can be performed first, followed by rapid bombardment; or bombardment can be performed simultaneously during the softening process.

[0047] As one possible implementation, softening the patterned photoresist and bombarding the patterned photoresist with plasma includes:

[0048] The pretreated substrate is placed in the cavity of a plasma stripper, the cavity is heated to soften the patterned photoresist, and the surface of the patterned photoresist is bombarded by plasma.

[0049] In this embodiment, a plasma stripper is used to simultaneously soften and bombard the patterned photoresist, which can improve the processing speed.

[0050] The cavity in the plasma resist stripper is heated, which softens the patterned photoresist. In this embodiment, the temperature of the cavity heating is not limited and depends on the specific circumstances.

[0051] As one possible implementation, the temperature range for heating the cavity is 70℃ to 80℃. For example, the heating temperature of the cavity can be 70℃, 74℃, 78℃, 80℃, etc.

[0052] If the cavity temperature is too low, the patterned photoresist may not soften sufficiently; if the cavity temperature is too high, the patterned photoresist may be too soft and unable to adjust the surface shape during plasma bombardment.

[0053] The plasma stripper is a microwave plasma source. It should be noted that in this embodiment, the power and bombardment time of the plasma stripper are not limited when bombarding the patterned photoresist; they can be set independently.

[0054] As one possible implementation, when bombarding the surface of the patterned photoresist with plasma, the power range of the plasma stripper is 200W to 500W, and the bombardment time ranges from 30s to 180s.

[0055] For example, the power of the plasma degumming machine can be 200W, 300W, 400W, 500W, etc.; the bombardment time can be 30s, 60s, 90s, 120s, 150s, 180s, etc.

[0056] By controlling the heating temperature at 70℃~80℃ and the bombardment time at 30s~180s, the relatively high temperature and short bombardment time can complete the planarization process while maintaining the overall morphology of the patterned photoresist, and at the same time avoid the accumulation of gas inside the photoresist, which would cause bubbles and voids.

[0057] It should also be noted that the gas used for bombardment is not limited in this embodiment and can be set by the user.

[0058] As one possible implementation method, the gases used for bombardment include oxidizing gases and fluorine-based gases, with a volume ratio of fluorine-based gases to oxidizing gases ranging from 1:1 to 1:3.

[0059] For example, the volume ratio of fluorine-based gas to oxidizing gas can be 1:1, 1:2, 1:3, etc.

[0060] Oxidizing gases can be oxygen (O2), etc., and fluorine-based gases can be carbon tetrafluoride (CF4), etc.

[0061] Step S103: Using the processed photoresist as a mask, etch the substrate to form an arc-shaped surface on the surface of the substrate, thereby obtaining an optical element with an arc-shaped surface.

[0062] The roughness of the curved surface of the optical element obtained in this embodiment is 0.6.

[0063] In this embodiment, the processing method obtains a pre-treated substrate including a substrate and a patterned photoresist. The surface of the patterned photoresist is curved. The patterned photoresist is softened to make the curved surface of the patterned photoresist flatter. During the softening process, plasma is used to bombard the curved surface, which can further promote the flattening of the curved surface. That is, a pre-treated photoresist with low roughness and a flatter surface can be obtained. Then, the pre-treated photoresist is used as a mask to etch the substrate, transferring the curved surface shape of the pre-treated photoresist to the substrate. This makes the roughness of the curved surface on the substrate relatively low, that is, an optical element with low surface roughness can be obtained.

[0064] Based on the above embodiments, in one embodiment of this application, obtaining the preprocessing substrate includes:

[0065] Photoresist is spin-coated onto the substrate;

[0066] The photoresist is pre-baked;

[0067] Laser direct writing exposure is performed on the photoresist after pre-baking;

[0068] Post-baking is performed on the exposed photoresist;

[0069] The post-baked photoresist is developed to form a patterned photoresist on the surface of the substrate.

[0070] It should be noted that the method of pre-baking the photoresist in this embodiment is not limited and can be set by the user.

[0071] In one embodiment of this application, pre-baking the photoresist includes:

[0072] The photoresist is heated to a first temperature.

[0073] The photoresist is further heated to a second temperature, which is higher than the first temperature.

[0074] In this embodiment, the photoresist is heated in two stages: first at a lower temperature, and then at a higher temperature. This can better relieve photoresist stress and effectively remove residual solvents inside the photoresist.

[0075] It should be noted that the first temperature and the second temperature are not limited in this embodiment and can be set by the user.

[0076] In one possible implementation, the first temperature is 65°C, and the heating time at the first temperature is 5 min to 15 min; the second temperature is 95°C, and the heating time at the second temperature is 5 min to 35 min.

[0077] In one embodiment of this application, before spin-coating the photoresist onto the substrate, the method further includes:

[0078] Clean the substrate to remove dirt from its surface.

[0079] The substrate can be cleaned sequentially with acetone, isopropanol, and deionized water, or other cleaning solutions can be used. This embodiment does not limit the specific cleaning solution used, as long as the dirt on the substrate surface can be removed.

[0080] Ultrasonic cleaning can be used to improve the cleanliness level.

[0081] In this embodiment, by thoroughly removing the dirt from the substrate surface, the bonding strength between the substrate and the patterned photoresist can be improved, preventing the patterned photoresist from detaching.

[0082] Based on any of the above embodiments, in one embodiment of this application, using the processed photoresist as a mask to etch the substrate to form an arc-shaped surface on the surface of the substrate may include:

[0083] The substrate is etched using the treated photoresist as a mask, and the curved surface morphology of the treated photoresist is copied to the surface of the substrate at a 1:1 ratio to form an arc-shaped surface on the surface of the substrate. The etching gas includes CHF3, inert gas, SF6 and O2, and the volume ratio of CHF3, inert gas, SF6 and O2 is in the range of (30-60):(30-60):(1-10):(10-30).

[0084] The inert gas can be argon (Ar) or similar, but this embodiment does not specify a particular gas.

[0085] By setting the volume ratio of the etching gas, the morphology of the photoresist can be replicated onto the substrate at a 1:1 ratio, reducing the roughness of the substrate surface.

[0086] In this embodiment, the substrate is etched using an ICP (Inductively Coupled Plasma)-RIE (Reactive Ion Etching) device, which includes two radio frequency sources with powers of 600W and 60W respectively. The etching is performed at atmospheric pressure (0.8Pa) and the substrate temperature is 0°C.

[0087] The processing method in this application will be described below using a specific example.

[0088] Step 1, as follows Figure 2 As shown, the silicon wafer substrate was cleaned sequentially using acetone, isopropanol, and deionized water via ultrasonic cleaning to obtain a clean substrate 1.

[0089] Step 2, as follows Figure 2 As shown, photoresist 2 is spin-coated on the upper surface of substrate 1 and pre-baked. The type of photoresist 2 can be AZ4562 and the thickness can be 27 micrometers. During pre-baking, the temperature is first raised to 65°C for 5 min to 15 min, and then raised to 95°C for 5 min to 35 min.

[0090] Step 3, as follows Figure 2 As shown, a laser is used to perform grayscale direct writing on photoresist 2, followed by baking and development to form a patterned photoresist 3 with an arc-shaped columnar structure. The bottom width of the arc-shaped columnar photoresist is d = 200 μm and the height is s = 10 μm.

[0091] Step 4, as follows Figure 2As shown, the plasma resist stripper is set to a power of 400W. The substrate 1 with patterned photoresist 3 is placed in the plasma resist stripper. The plasma resist stripper is preheated to planarize the curved surface of the photoresist. During the heating process, O2 and CF4 are used to bombard the surface of the patterned photoresist 3 to further promote planarization and reduce the roughness of the curved surface of the patterned photoresist 3, achieving a roughness of <1nm. The volume ratio of O2 to CF4 is 7:5.

[0092] Step 5, as follows Figure 2 As shown, the patterned photoresist 3 is transferred and etched onto the substrate in a 1:1 ratio using an ICP-RIE device. The power of the radio frequency source is set to 600W and 60W, the substrate temperature is 0℃, and the pressure is atmospheric pressure. CHF3, Ar, SF6, and O2 are used for etching, with a volume ratio of CHF3, Ar, SF6, and O2 of 40:40:3:17. This maintains the surface roughness of the patterned photoresist, achieving atomic-level flatness (roughness <1nm) on the arc surface of the substrate 4 after etching.

[0093] This application also provides an optical element with an arcuate surface, wherein the optical element with an arcuate surface is obtained by the processing method of the optical element with an arcuate surface described in any of the above embodiments.

[0094] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. The above provides a detailed description of the optical element with an arc-shaped surface and its processing method provided in this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the embodiments above are only for the purpose of helping to understand the solution and core ideas of this application. It should be noted that those skilled in the art can make several improvements and modifications to this application without departing from the principles of this application, and these improvements and modifications also fall within the protection scope of this application.

Claims

1. A method of processing an optical element having an arc-shaped curved surface, characterized by, The method comprises the following steps: obtaining a pretreated substrate, the pretreated substrate comprising a substrate and a patterned photoresist on the surface of the substrate, the patterned photoresist being arc-shaped away from the surface of the substrate; softening the patterned photoresist and bombarding the patterned photoresist with plasma to form a treated photoresist, the treated photoresist being arc-shaped away from the surface of the substrate; using the treated photoresist as a mask to etch the substrate to form an arc-shaped surface on the surface of the substrate, thereby obtaining an optical element with an arc-shaped surface; the step of softening the patterned photoresist and bombarding the patterned photoresist with plasma comprises the following steps: placing the pretreated substrate in a cavity of a plasma stripping machine, controlling the temperature of the cavity to soften the patterned photoresist, and bombarding the surface of the patterned photoresist with plasma, the temperature of the cavity being in the range of 70-80℃.

2. The method of processing an optical element having an arcuate surface as recited in claim 1, wherein, when bombarding the surface of the patterned photoresist with plasma, the power of the plasma stripping machine is in the range of 200-500W, and the bombarding time is in the range of 30-180s; and / or, the gas used for bombarding comprises an oxidizing gas and a fluorine-based gas, and the volume ratio of the fluorine-based gas to the oxidizing gas is in the range of 1:1-1:

3.

3. The method of claim 1, wherein the optical element having an arc surface is a lens. the step of using the treated photoresist as a mask to etch the substrate to form an arc-shaped surface on the surface of the substrate comprises the following steps: using the treated photoresist as a mask to etch the substrate, and copying the curved surface morphology of the treated photoresist to the surface of the substrate in a 1:1 ratio to form an arc-shaped surface on the surface of the substrate, wherein the etching gas comprises CHF3, an inert gas, SF6 and O2, and the volume ratio of CHF3, the inert gas, SF6 and O2 is (30-60):(30-60):(1-10):(10-30).

4. The method of claim 1, wherein the optical element having an arc surface is a lens. the step of obtaining a pretreated substrate comprises the following steps: spinning photoresist on the substrate; pre-baking the photoresist; laser direct writing exposure to the pre-baked photoresist; post-baking the exposed photoresist; and developing the post-baked photoresist to form a patterned photoresist on the surface of the substrate.

5. The method of claim 4, wherein the optical element having an arc-shaped curved surface is a lens. Before spinning photoresist on the substrate, the method further comprises the following step: cleaning the substrate to remove dirt on the surface of the substrate.

6. The method of processing an optical element having an arcuate surface as recited in claim 4, wherein, the step of pre-baking the photoresist comprises the following steps: heating the photoresist at a first temperature; and continuing to heat the photoresist at a second temperature, the second temperature being higher than the first temperature.

7. The method of processing an optical element having an arcuate surface as recited in claim 6, wherein, the first temperature is 65℃, and the heating time at the first temperature is 5-15min; the second temperature is 95℃, and the heating time at the second temperature is 5-35min.

8. An optical element having an arcuate curved surface, characterized by, the optical element with an arc-shaped surface is obtained by the method for processing an optical element with an arc-shaped surface according to any one of claims 1-7.

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