Optical element with arc-shaped curved surface and processing method thereof

Abstract

The invention relates to the field of optical element processing, and discloses an optical element with an arc-shaped curved surface and a processing method thereof.The processing method comprises the steps that a pretreatment substrate is obtained, the pretreatment substrate comprises a substrate body and graphical photoresist located on the surface of the substrate body, and the surface, away from the substrate body, of the graphical photoresist is the arc-shaped curved surface; the patterned photoresist is softened, the patterned photoresist is bombarded through plasma, processed photoresist is formed, and the surface, away from the substrate, of the processed photoresist is an arc-shaped curved surface; and etching the substrate by taking the processed photoresist as a mask, and forming an arc-shaped curved surface on the surface of the substrate to obtain the optical element with the arc-shaped curved surface. By softening the patterned photoresist and bombarding the arc-shaped surface by using the plasma, the surface of the patterned photoresist can be flattened, the treated photoresist is used as a mask to etch the substrate, and the surface shape of the arc-shaped surface of the treated photoresist is transferred to the substrate, so that the roughness of the arc-shaped surface on the substrate is reduced.

Description

Technical Field

[0001] The present application relates to the field of optical element processing, and in particular to an optical element with a curved surface and a processing method thereof. Background Art

[0002] Optical elements with curved surfaces (such as microlenses or microlens arrays) are widely used in optical charge-coupled devices, digital projectors, optical microscopes, smartphone cameras and other devices. The roughness of the curved surface of the optical element has an important influence on the effect of the optical element.

[0003] The preparation method based on laser grayscale lithography and dry etching process is a process that can mass-produce optical components with highly uniform curved surfaces. A patterned photoresist mask is formed on a substrate by photoresist, and then the substrate is etched to form a curved surface. However, the roughness of the curved surface manufactured by this processing method is relatively large, with a roughness of about 5, which affects the effect of the optical component.

[0004] Therefore, how to reduce the roughness of the arc-shaped surface on the optical element should be a technical problem that needs to be solved urgently by those skilled in the art. Summary of the invention

[0005] The purpose of the present application is to provide an optical element with a curved surface and a processing method thereof, so as to reduce the roughness of the curved surface on the optical element.

[0006] In order to solve the above technical problems, the present application provides a method for processing an optical element having a curved surface, comprising:

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

[0008] Softening the patterned photoresist and bombarding the patterned photoresist with plasma to form a processed photoresist, wherein the surface of the processed photoresist away from the substrate is an arc-shaped curved surface;

[0009] The substrate is etched using the treated 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 pre-treated substrate is placed in a cavity of a plasma stripping machine, the cavity is controlled to increase in temperature to soften the patterned photoresist, and the surface of the patterned photoresist is bombarded by plasma.

[0012] Optionally, the temperature range of the cavity heating is 70°C to 80°C.

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

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

[0015] Optionally, etching the substrate using the treated photoresist as a mask to form an arc-shaped surface on the surface of the substrate comprises:

[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 ratio of 1:1 to form an arc-shaped curved surface on the surface of the substrate, wherein the etching gas includes CHF3, an inert gas, SF6 and O2, and the volume ratio of CHF3, the inert gas, SF6 and O2 ranges from (30 to 60): (30 to 60): (1 to 10): (10 to 30).

[0017] Optionally, obtaining the pretreated substrate comprises:

[0018] Spin coating photoresist on the substrate;

[0019] Pre-baking the photoresist;

[0020] Perform laser direct writing exposure on the pre-baked photoresist;

[0021] Post-baking 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 on the substrate, the method further comprises:

[0024] The substrate is cleaned to remove dirt on the surface of the substrate.

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

[0026] heating the photoresist at a first temperature;

[0027] The photoresist is continuously heated by increasing the temperature 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] The present application also provides an optical element with a curved surface, and the optical element with a curved surface is obtained by using any of the above-mentioned processing methods for an optical element with a curved surface.

[0030] The present application provides a method for processing an optical element with a curved surface, comprising: obtaining a pre-treated substrate, the pre-treated substrate comprising a substrate and a patterned photoresist located on the surface of the substrate, the surface of the patterned photoresist away from the substrate being a 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 a curved surface; etching the substrate using the treated photoresist as a mask to form a curved surface on the surface of the substrate, thereby obtaining an optical element with a curved surface.

[0031] It can be seen that the processing method in the present application obtains a pre-treated 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, and plasma is used to bombard the arc-shaped surface during the softening process, which can further promote the flattening of the arc-shaped surface, that is, a treated photoresist with low roughness and a flatter surface can be obtained, and then the substrate is etched using the treated photoresist as a mask, and the arc-shaped surface shape of the treated photoresist is transferred to the substrate, so that the roughness of the arc-shaped surface on the substrate is also relatively low, that is, an optical element with relatively low surface roughness can be obtained.

[0032] In addition, the present application also provides an optical element with a curved surface having the above advantages. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present application or the technical solutions of the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0034] Figure 1 A flowchart of a method for processing an optical element with a curved surface provided in an embodiment of the present application;

[0035] Figure 2A process flow chart of a method for processing an optical element with a curved surface provided in an embodiment of the present application. DETAILED DESCRIPTION

[0036] In order to enable those skilled in the art to better understand the present application, the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present application.

[0037] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0038] As described in the background technology section, when preparing an optical element with a curved surface, a patterned photoresist mask is formed on a substrate by photoresist, and then the substrate is etched to form a curved surface. However, the roughness of the curved surface manufactured by this processing method is relatively large, with a roughness of about 5, which affects the effect of the optical element.

[0039] In view of this, the present application provides a method for processing an optical element with a curved surface, please refer to Figure 1 , the method comprising:

[0040] Step S101: obtaining a pre-treated substrate, wherein the pre-treated substrate comprises a substrate and a patterned photoresist located on a surface of the substrate, wherein a surface of the patterned photoresist away from the substrate is an arc-shaped curved surface.

[0041] The substrate may be a substrate of other materials such as a silicon wafer, and is not specifically limited in this embodiment.

[0042] It should be noted that the method for obtaining the pre-treated substrate is not limited in this embodiment and can be selected at will. A pre-treated substrate that has been manufactured can be directly used, or a pre-treated substrate can be manufactured at will.

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

[0044] The patterned photoresist can make the curved surface of the photoresist flatter during the softening process, and the bombardment with plasma can further promote the planarization process of the photoresist.

[0045] It should be emphasized that in this step, the photoresist is softened, not thermally reflowed. The hardness of the softened photoresist is greater than that of the photoresist subjected to thermal reflow treatment. When bombarded, it can not only promote flattening, but also adjust the surface angle of the curved surface.

[0046] It should be noted that the present embodiment does not limit the method of softening the patterned photoresist and bombarding the patterned photoresist. For example, the patterned photoresist may be softened first and then bombarded quickly; or bombarded simultaneously during the softening process.

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

[0048] The pre-treated substrate is placed in a cavity of a plasma stripping machine, the cavity is controlled to increase in temperature 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 process the softening and bombardment of the patterned photoresist, which can increase the processing speed.

[0050] The temperature of the cavity in the plasma stripper is increased, that is, the patterned photoresist is heated, so that the patterned photoresist is softened. In this embodiment, the temperature of the cavity is not limited and depends on the situation.

[0051] As an implementation method, the temperature range of the cavity heating is 70° C. to 80° C. Exemplarily, the cavity heating temperature can be 70° C., 74° C., 78° C., 80° C., etc.

[0052] If the temperature of the chamber heating is too low, the patterned photoresist may not be softened enough; if the temperature of the chamber heating 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, when bombarding the patterned photoresist, the power and bombardment time of the plasma stripper are not limited and can be set by oneself.

[0054] As an implementation method, when the surface of the patterned photoresist is bombarded by plasma, the power range of the plasma stripper is 200W to 500W, and the bombardment time range is 30s to 180s.

[0055] Exemplarily, 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°C to 80°C and the bombardment time at 30s to 180s, the temperature is relatively high and the bombardment time is short, the flattening process can be completed while maintaining the overall morphology of the patterned photoresist, while avoiding the accumulation of gas inside the photoresist to produce 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 oneself.

[0058] As an implementable method, the gas used for bombardment includes an oxidizing gas and a fluorine-based gas, and the volume ratio of the fluorine-based gas to the oxidizing gas ranges from 1:1 to 1:3.

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

[0060] The oxidizing gas may be oxygen (O2) or the like, and the fluorine-based gas may be carbon tetrafluoride (CF4) or the like.

[0061] Step S103: etching the substrate using the treated photoresist as a mask to form an arc-shaped surface on the surface of the substrate, thereby obtaining an optical element having an arc-shaped surface.

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

[0063] In the processing method of this embodiment, a pre-treated substrate including a substrate and a patterned photoresist is obtained, and 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, and plasma is used to bombard the arc-shaped surface during the softening process to further promote the flattening of the arc-shaped surface, that is, a treated photoresist with low roughness and a flatter surface can be obtained, and then the substrate is etched using the treated photoresist as a mask to transfer the arc-shaped surface shape of the treated photoresist to the substrate, so that the roughness of the arc-shaped surface on the substrate is also relatively low, that is, an optical element with relatively low surface roughness can be obtained.

[0064] Based on the above embodiments, in one embodiment of the present application, obtaining a pretreated substrate comprises:

[0065] Spin coating photoresist on the substrate;

[0066] Pre-baking the photoresist;

[0067] Perform laser direct writing exposure on the pre-baked photoresist;

[0068] Post-baking 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 pointed out that the method of pre-baking the photoresist is not limited in this embodiment and can be set by oneself.

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

[0072] heating the photoresist at a first temperature;

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

[0074] In this embodiment, the photoresist is heated twice, first at a lower temperature and then at a higher temperature, which can better remove the stress of the photoresist and effectively remove the residual solvent inside the photoresist.

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

[0076] As an implementable embodiment, 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 the present application, before spin coating the photoresist on the substrate, the method further comprises:

[0078] The substrate is cleaned to remove dirt on the surface of the substrate.

[0079] The substrate may be cleaned in sequence using acetone, isopropanol, and deionized water, or may be cleaned using other cleaning solutions, which are not limited in this embodiment, as long as the dirt on the surface of the substrate can be removed.

[0080] The cleaning method can be ultrasonic cleaning to improve the cleaning level.

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

[0082] On the basis of any of the above embodiments, in one embodiment of the present application, etching the substrate using the treated photoresist as a mask 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 ratio of 1:1 to form an arc-shaped curved surface on the surface of the substrate, wherein the etching gas includes CHF3, an inert gas, SF6 and O2, and the volume ratio of CHF3, the inert gas, SF6 and O2 ranges from (30 to 60): (30 to 60): (1 to 10): (10 to 30).

[0084] The inert gas may be argon (Ar) gas or the like, which is not specifically limited in this embodiment.

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

[0086] In this embodiment, the substrate is etched using ICP (Inductively Couple Plasma)-RIE (Reactive Ion Etching) equipment, which includes two RF sources, the powers of the RF sources can be 600W and 60W respectively, the etching is carried out under normal pressure (0.8Pa), and the substrate temperature is 0°C.

[0087] The processing method in this application is described below with reference to a specific case.

[0088] Step 1: Figure 2 As shown, the silicon wafer substrate is cleaned in sequence using acetone, isopropanol, and deionized water by ultrasonic cleaning to obtain a clean substrate 1;

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

[0090] Step 3: Figure 2 As shown, a laser is used to perform grayscale direct writing on the photoresist 2, and then post-baking and developing are performed to form a patterned photoresist 3 with an arc-shaped columnar structure, wherein the bottom width d of the arc-shaped columnar photoresist is 200 μm and the height s is 10 μm;

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

[0092] Step 5: Figure 2 As shown, the surface shape of the patterned photoresist 3 is transferred and etched onto the substrate in a 1:1 manner. Using ICP-RIE equipment, the powers of the RF source are set to 600 W and 60 W, respectively, the substrate temperature is 0°C, the pressure is normal pressure, and CHF3, Ar, SF6 and O2 are used for etching. The volume ratio of CHF3, Ar, SF6 and O2 is 40:40:3:17. The roughness of the surface of the patterned photoresist is maintained, and the arc surface on the substrate 4 after etching is atomically flat (roughness <1 nm).

[0093] The present application also provides an optical element with a curved surface, and the optical element with a curved surface is obtained by using the processing method of the optical element with a curved surface described in any of the above embodiments.

[0094] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. The optical element with a curved surface and a processing method thereof provided by the present application are described in detail above. Specific examples are used in this article to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the scheme of the present application and its core idea. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present application, several improvements and modifications can be made to the present application, and these improvements and modifications also fall within the scope of protection of the present application.

Claims

1. A method for processing an optical element having a curved surface, characterized in that: include: Obtaining a pre-treated substrate, the pre-treated substrate comprising a substrate and a patterned photoresist located on a surface of the substrate, wherein a surface of the patterned photoresist away from the substrate is an arc-shaped curved surface; Softening the patterned photoresist and bombarding the patterned photoresist with plasma to form a processed photoresist, wherein the surface of the processed photoresist away from the substrate is an arc-shaped curved surface; The substrate is etched using the treated 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.

2. The method for processing an optical element having a curved surface according to claim 1, characterized in that: Softening the patterned photoresist and bombarding the patterned photoresist with plasma comprises: The pre-treated substrate is placed in a cavity of a plasma stripping machine, the cavity is controlled to increase in temperature to soften the patterned photoresist, and the surface of the patterned photoresist is bombarded by plasma.

3. The method for processing an optical element having a curved surface according to claim 2, wherein: The temperature range of the cavity heating is 70°C to 80°C.

4. The method for processing an optical element having a curved surface according to claim 2, wherein: When the surface of the patterned photoresist is bombarded by plasma, the power range of the plasma stripper is 200W to 500W, and the bombardment time range is 30s to 180s; and / or, The gases used for bombardment include oxidizing gas and fluorine-based gas, and the volume ratio of the fluorine-based gas to the oxidizing gas ranges from 1:1 to 1:

3.

5. The method for processing an optical element having a curved surface according to claim 1, wherein: 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 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 ratio of 1:1 to form an arc-shaped curved surface on the surface of the substrate, wherein the etching gas includes CHF3, an inert gas, SF6 and O2, and the volume ratio of CHF3, the inert gas, SF6 and O2 ranges from (30 to 60): (30 to 60): (1 to 10): (10 to 30).

6. The method for processing an optical element having a curved surface according to claim 1, wherein: Obtaining a pre-treated substrate includes: Spin coating photoresist on the substrate; Pre-baking the photoresist; Perform laser direct writing exposure on the pre-baked photoresist; Post-baking the exposed photoresist; The post-baked photoresist is developed to form a patterned photoresist on the surface of the substrate.

7. The method for processing an optical element having a curved surface according to claim 6, wherein: Before spin coating the photoresist on the substrate, the method further comprises: The substrate is cleaned to remove dirt on the surface of the substrate.

8. The method for processing an optical element having a curved surface according to claim 6, wherein: Pre-baking the photoresist comprises: heating the photoresist at a first temperature; The photoresist is continuously heated by increasing the temperature to a second temperature, which is higher than the first temperature.

9. The method for processing an optical element having a curved surface according to claim 8, wherein: 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.

10. An optical element having a curved surface, characterized in that: The optical element with a curved surface is obtained by using the processing method of an optical element with a curved surface as claimed in any one of claims 1 to 9.

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