CN113484940B

CN113484940B - Micro-lens array, preparation method thereof and vertical cavity surface emitting laser structure

Info

Publication number: CN113484940B
Application number: CN202110756538.5A
Authority: CN
Inventors: 苗霈; 刘恒; 王俊; 刘畅; 肖垚; 谷飞
Original assignee: Suzhou Everbright Photonics Co Ltd; Suzhou Everbright Semiconductor Laser Innovation Research Institute Co Ltd
Current assignee: Suzhou Everbright Photonics Co Ltd; Suzhou Everbright Semiconductor Laser Innovation Research Institute Co Ltd
Priority date: 2021-07-05
Filing date: 2021-07-05
Publication date: 2023-05-23
Anticipated expiration: 2041-07-05
Also published as: CN113484940A

Abstract

The invention discloses a micro lens array, a preparation method thereof and a vertical cavity surface emitting laser structure, wherein the method comprises the following steps: forming a photoresist mask in a microlens shape on a first surface of a substrate; and etching the photoresist mask and the substrate by adopting a dry etching process based on etching gas and passivation gas, so that the substrate forms a microlens array with a preset shape, and adjusting the proportion of the passivation gas in the dry etching process, so that the etching selectivity ratio value is gradually reduced. By implementing the invention, a photoresist mask is formed on a substrate, and dry etching is carried out on the photoresist mask and the substrate to obtain a micro lens array; in the dry etching process, the selection ratio of the dry etching is changed by adding the passivation gas, and meanwhile, in the dry etching process, the selection ratio of the etching is gradually reduced by adjusting the proportion of the passivation gas, namely, a step-by-step etching mode is adopted, different selection ratios are adopted in each step, and finally, the high-quality microlens array with good collimation effect is obtained.

Description

Micro-lens array, preparation method thereof and vertical cavity surface emitting laser structure

Technical Field

The invention relates to the technical field of laser preparation, in particular to a micro-lens array, a preparation method thereof and a vertical cavity surface emitting laser structure.

Background

Vertical-Cavity Surface-Emitting Laser (VCSEL) arrays are increasingly becoming an important light source for a range of high optical power applications such as 3D sensing, lidar, night vision illumination, health care, etc. VCSEL arrays offer advantages over stacked edge-emitting laser arrays in terms of scalability, uniformity, yield, and optical integration. Conventional oxide-confined VCSELs typically have an aperture of less than 50 μm to achieve uniform current injection and optimal optical mode confinement, when 1/e of the laser ² The divergence (total) angle ranges from 10 DEG to<50 deg.. Because the beam divergence of a vcsels is inversely proportional to its beam waist, the large beam divergence inherent in an oxide-confined vcsels can reduce far-field beam distribution, severely limiting the working distance of the vcsels integrated system. Therefore, it is common practice to integrate micro-optical components such as microlenses within a range of several tens of micrometers from the VCSEL light exit window, optimizing the divergence (full) angle of the light beam to below 10 °, improving the collimation of the light beam.

The currently prevailing microlens fabrication methods basically include three types. One is a droplet ejection method, in which uv-curable polymer droplet nozzles are printed on a substrate and then uv-cured to form microlenses. And secondly Polydimethylsiloxane (PDMS) molding techniques, involving thermal and pressure manipulation, require movement and alignment to the device chip during production. Thirdly, negative chemical amplification photoresist (such as SU-8, SAL601 and the like) is used as a manufacturing material of a smooth curved surface microstructure, and photo-acid isotropic diffusion is utilized to catalyze photoresist molecules of an exposure area and adjacent diffusion areas thereof to crosslink.

However, for the current preparation process of the micro-lens, the adjustable range of the curvature of the micro-lens is limited from the perspective of the collimation performance of the micro-lens, and the micro-lens with higher collimation effect cannot be obtained.

Disclosure of Invention

In view of the above, embodiments of the present invention provide a microlens array, a preparation method thereof, and a vertical cavity surface emitting laser structure, so as to solve the technical problem that a microlens preparation process in the prior art cannot obtain a microlens array with a higher collimation effect.

The technical scheme provided by the embodiment of the invention is as follows:

an embodiment of the present invention provides a method for manufacturing a microlens array, including: forming a photoresist mask in a microlens shape on a first surface of a substrate; and etching the photoresist mask and the substrate by adopting a dry etching process based on etching gas and passivation gas, so that the substrate forms a microlens array with a preset shape, and adjusting the proportion of the passivation gas in the dry etching process to gradually reduce the etching selection ratio value.

Optionally, the passivation gas includes CHF ₃ And N ₂ The dry etching process comprises the following steps: three stages; in the first stage of etching, a passivation gas CHF ₃ And N ₂ The flow ratio of (2) is 6:1-4:1; in the second stage of etching, the passivation gas CHF ₃ And N ₂ The flow ratio of (2) is 1:1-1:3; in the third stage of etching, the passivation gas CHF ₃ And N ₂ The flow ratio of (2) is 1:4-1:6.

Optionally, in the second phase of etching, the dry etching includes four steps, the first step of passivating the gaseous CHF ₃ And N ₂ The flow ratio of (2) is 1:1, and the first step of passivation gas CHF ₃ And N ₂ The flow ratio of (2) is 1:2, and the first step of passivation gas CHF ₃ And N ₂ The flow ratio of (2) to (5), the first passivation gas CHF ₃ And N ₂ The flow ratio of (2) to (7).

Optionally, the dry etching process includes: three stages; in the first stage of etching, the etching selectivity ratio is more than 19 and less than 21; in the second stage of etching, the ratio of etching selectivity is more than 2 and less than 18; in the third stage of etching, the ratio of etching selectivity is more than 0.2 and less than 1.

Optionally, in the second stage of etching, the dry etching includes four steps, the first step selection ratio is greater than 15 and less than 18, the second step selection ratio is greater than 11 and less than 14, the third step selection ratio is greater than 7 and less than 10, and the fourth step selection ratio is greater than 3 and less than 6.

Alternatively, the center thickness of the pre-shaped microlens array is 30 micrometers to 40 micrometers and the radius of curvature is 250 micrometers to 300 micrometers.

Optionally, forming a microlens-shaped photoresist mask on the first surface of the substrate, comprising: spin-coating photoresist on the first surface of the substrate, and performing pre-baking; placing a photoetching plate on the surface of photoresist far away from the substrate, exposing and developing the photoresist; and performing post-baking and thermal reflux plasticity on the photoresist subjected to exposure and development to obtain the photoresist mask in the shape of the microlens.

Optionally, before forming the microlens-shaped photoresist mask on the first surface of the substrate, comprising: sequentially forming a first distributed feedback Bragg reflector, an active region and a second distributed feedback Bragg reflector on a second surface of a substrate, wherein the second surface is another surface which is arranged opposite to the first surface on the substrate; and processing the substrate to obtain the substrate with the preset thickness.

A second aspect of the embodiment of the present invention provides a microlens array, which is characterized in that the microlens array is prepared by using the preparation method of the microlens array according to the first aspect of the embodiment of the present invention and any one of the first aspect of the embodiment of the present invention.

A third aspect of an embodiment of the present invention provides a vertical cavity surface emitting laser structure, including: a substrate; the micro-lens array is positioned on the first surface of the substrate, and is prepared by adopting the preparation method of the micro-lens array according to the first aspect of the embodiment and part of the embodiments of the first aspect; the first distributed feedback Bragg reflector, the active region and the second distributed feedback Bragg reflector are sequentially arranged on the second surface of the substrate, and the second surface is the other surface, which is arranged opposite to the first surface, of the substrate.

The technical scheme of the invention has the following advantages:

the preparation method of the micro lens array provided by the embodiment of the invention comprises the steps of forming a photoresist mask on a substrate, and carrying out dry etching on the photoresist mask and the substrate to obtain the micro lens array; in the dry etching process, the selection ratio of the dry etching is changed by adding the passivation gas, and meanwhile, in the dry etching process, the selection ratio of the etching is gradually reduced by adjusting the proportion of the passivation gas, namely, a step-by-step etching mode is adopted, different selection ratios are adopted in each step, and finally, the high-quality microlens array with good collimation effect is obtained.

According to the preparation method of the microlens array, provided by the embodiment of the invention, the passivation gas is added in the preparation process, and meanwhile, a stepwise process is adopted, so that the operation flow is simple and easy to control, the required steps are few, the preparation method has a good beam collimation effect, and the preparation method is suitable for mass production of VCSEL devices with special functions.

The microlens array provided by the embodiment of the invention is prepared by adopting a dry etching process of adding passivation gas and step etching, so that the microlens has a good collimation effect, and is suitable for being applied to mass production of vertical cavity surface emitting lasers.

According to the vertical cavity surface emitting laser structure provided by the embodiment of the invention, the micro lens array is prepared by adopting a dry etching process of adding passivation gas and step etching, so that the vertical cavity surface emitting laser has a better beam collimation effect. Is suitable for mass production.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are needed in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below are some embodiments of the present invention, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.

FIG. 1 is a flowchart of a method for manufacturing a microlens array according to an embodiment of the present invention;

FIG. 2 is a flow chart of a method for fabricating a microlens array according to another embodiment of the present invention;

FIG. 3 is a schematic diagram of a structure after spin-coating photoresist according to an embodiment of the present invention;

FIG. 4 is a schematic view of an ultraviolet exposure structure according to an embodiment of the present invention;

FIG. 5 is a schematic diagram of a photoresist mask formed according to an embodiment of the present invention;

fig. 6 is a schematic structural diagram of a microlens array formed in an embodiment of the present invention.

Detailed Description

The following description of the embodiments of the present invention will be made apparent and fully in view of the accompanying drawings, in which some, but not all embodiments of the invention are shown. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

In the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. are based on the directions or positional relationships shown in the drawings, are merely for convenience of describing the present invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the description of the present invention, it should be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be either fixedly connected, detachably connected, or integrally connected, for example; can be mechanically or electrically connected; the two components can be directly connected or indirectly connected through an intermediate medium, or can be communicated inside the two components, or can be connected wirelessly or in a wired way. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.

In addition, the technical features of the different embodiments of the present invention described below may be combined with each other as long as they do not collide with each other.

Example 1

The embodiment of the invention provides a preparation method of a micro lens array, as shown in fig. 1, comprising the following steps:

step S101: a microlens-shaped photoresist mask is formed on a first surface of a substrate.

In one embodiment, the photoresist mask may be prepared according to the following process: spin-coating photoresist on the first surface of the substrate, and performing pre-baking; placing a photoetching plate on the surface of photoresist far away from a substrate, exposing and developing the photoresist; and performing post-baking and thermal reflux plasticity on the photoresist subjected to exposure and development to obtain the photoresist mask in the shape of the microlens.

Specifically, a spin coating process may be used to spin-coat a photoresist positive photoresist on the first surface of the substrate, and then a pre-bake is performed, during which the excess solvent in the photoresist film is driven away and exposed to ultraviolet light, and the photodecomposition process of the photoresist polymer begins. After baking, the photoresist plate is placed on the surface of the photoresist, which is far away from the substrate, and then ultraviolet light is used for irradiating the photoresist which is partially shielded by the photoresist plate to realize the exposure process. Wherein the reticle may be pre-designed according to the desired position and configuration of the microlens array. Thus, during exposure, the portion masked by the lithographic plate is protected for subsequent processing. After ultraviolet exposure is completed, a large-area photoresist mask structure is formed through post baking, thermal reflux and other processes and is used for a subsequent dry etching process.

Step S102: and etching the photoresist mask and the substrate by adopting a dry etching process based on etching gas and passivation gas, so that the substrate forms a microlens array with a preset shape, and adjusting the proportion of the passivation gas in the dry etching process, so that the etching selectivity ratio value is gradually reduced.

In one embodiment, after the photoresist mask is obtained, a dry etching process of RIE-ICP, that is, an etching process based on inductively coupled plasma is used to etch the substrate and the photoresist mask until the photoresist mask is completely etched, thereby transferring the designed microlens morphology to the substrate to obtain the microlens array with the preset shape.

In one embodiment, when the fabricated microlens array is integrated as a micro-assembly in the light exit window of the laser, the microlens array is required to have good collimation effect. In the dry etching process adopted in the prior art, etching gases such as BCl are mostly adopted ₃ And Cl ₂ And the like, etching is performed while maintaining a fixed etching selectivity. Also, in practical process experiments, only thinner photoresist can be used as a mask because the radius of curvature of thick photoresist is greatly reduced. Thinner photoresists require a higher selectivity of the dry etch. However, if a higher selection ratio is used throughout the dry etching process, the radii of curvature (Radius of Curvature, roc) of the microlens structures are too small to achieve a good collimation effect.

Therefore, in the dry etching process, on the premise of keeping the etching gas unchanged, the passivation gas is added to adjust the etching selection ratio. Meanwhile, in the etching process, the proportion of the passivation gas is adjusted to enable the etching selection ratio to be changed continuously, namely, the photoresist mask and the substrate are etched in a mode of non-fixed etching ratio. Specifically, a higher selection ratio is selected in the early stage of etching; in the middle stage of etching, selecting a selection ratio of a middle value; in the latter stage of etching, a smaller etching ratio is selected. And finally, after the etching is finished, obtaining the microlens array with the preset shape.

As an alternative implementation of the embodiment of the invention, in order to gradually reduce the etching selection ratio in the dry etching process, the method canIn a step-by-step etching manner, different selection ratios are achieved by using different ratios of passivation gases during each step. In one embodiment, the short-term gas includes CHF ₃ And N ₂ The dry etching is divided into three phases, in the first phase of etching, the passivation gas CHF ₃ And N ₂ The flow ratio of (2) is 6:1-4:1; in the second stage of etching, the passivation gas CHF ₃ And N ₂ The flow ratio of (2) is 1:1-1:3; in the third stage of etching, the passivation gas CHF ₃ And N ₂ The flow ratio of (2) is 1:4-1:6. Wherein, in the first stage, the passivation gas CHF ₃ And N ₂ The flow ratio of (2) may be 6:1,5:1 or 4:1, etc. In the second stage, the passivation gas CHF ₃ And N ₂ The flow ratio of (2) may be 1:1,1:2,2:5,1:3,2:7,1:3, etc. In the third stage, passivation gas CHF ₃ And N ₂ The flow ratio of (2) may be 1:4,2:9,1:5 or 1:6, etc.

Specifically, at each stage, the passivation gas CHF ₃ And N ₂ The dry etching process may be completed by using any of the above-mentioned ratios. I.e., during dry etching, the passivation gas CHF can be adjusted ₃ And N ₂ Three sequentially reduced ratios are obtained for the flow ratio of the dry etching step by step etching. For the three stages of the above division, the division may be performed according to the total duration of dry etching, for example, the first 1/3 stage of the total duration of etching is the first stage, the middle 1/3 stage of the total duration of etching is the second stage, and the second 1/3 stage of the total duration of etching is the third stage.

Specifically, in order to further reduce the influence of abrupt change of the flow ratio on the interface state on the morphology of the microlens, the second stage of dry etching can be divided into four steps again. Wherein, the first step of passivation gas CHF ₃ And N ₂ The flow ratio of (2) is 1:1, and the first step of passivation gas CHF ₃ And N ₂ The flow ratio of (2) is 1:2, and the first step of passivation gas CHF ₃ And N ₂ The flow ratio of (2) to (5), the first passivation gas CHF ₃ And N ₂ The flow ratio of (2) to (7). Wherein the division of the four steps can also be according to the second stageAnd (5) carrying out average division on the total etching duration to obtain four steps.

Specifically, during dry etching, the passivation gas CHF may be determined in accordance with the flow ratio described above ₃ And N ₂ Is a specific flow rate of the gas. For example, in the first stage, the passivation gas CHF ₃ And N ₂ The flow rates of (2) are 10sccm and 2sccm, respectively, and in the second stage, the passivation gas CHF is used ₃ And N ₂ The flow rates of (1) are 10sccm and 10sccm, 5sccm and 10sccm, 2sccm and 5sccm, 2sccm and 7sccm, respectively. In the third stage, passivation gas CHF ₃ And N ₂ The flow rates of (2 sccm) and (10 sccm), respectively. Wherein, in the whole dry etching process, etching gas BCl ₃ And Cl ₂ The flow rate of (2) can be kept unchanged, such as BCl ₃ Is 20sccm, cl ₂ The flow rate of (2 sccm).

As an alternative implementation manner of the embodiment of the present invention, in three stages of dry etching, the etching selection ratio of each stage may be determined by adjusting the flow rate of the passivation gas by using the time sharing. Alternatively, the etching selectivity of each stage may be determined first, and then the flow rate of the passivation gas of each stage may be determined according to the determined selectivity. In one embodiment, in the first stage of etching, the ratio of etching selectivity is greater than 19 and less than 21; in the second stage of etching, the ratio of etching selectivity is more than 2 and less than 18; in the third stage of etching, the ratio of etching selectivity is more than 0.2 and less than 1. Wherein, in the first stage of etching, the ratio of etching selectivity can be 21, 20 or 19; in the second stage of etching, the ratio of the etching selectivity may be 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3,2, etc.; in the second stage of etching, the ratio of the etching selectivity may be 1, 0.5, 0.2, or the like.

Specifically, at each stage, the etching selectivity may be any one of the ratios mentioned above, and the dry etching process is completed. Namely, in the dry etching process, three sequentially reduced selection ratios can be adopted to carry out step etching of the dry etching. For the three stages of the above division, the division may also be performed according to the total duration of dry etching, for example, the first 1/3 stage of the total duration of etching is the first stage, the second stage is the middle 1/3 stage of the total duration of etching, and the third stage is the last 1/3 stage of the total duration of etching.

Specifically, in order to further reduce the influence of abrupt changes in the selectivity on the interface state on the morphology of the microlens, the second stage of dry etching can be divided into four steps again. The ratio of the first step is more than 15 and less than 18, the ratio of the second step is more than 11 and less than 14, the ratio of the third step is more than 7 and less than 10, and the ratio of the fourth step is more than 3 and less than 6. Wherein, the ratio of the first step selection ratio can be 18, 17, 16 or 15, etc.; the ratio of the second step selection ratio may be 14, 13, 12 or 11, etc.; the ratio of the selection ratio of the third step can be 10, 9, 8 or 7, etc.; the ratio of the fourth step selection ratio may be 6, 5, 4, 3, or the like.

Specifically, during the dry etching, the final selection ratio may be selectively determined according to the above ratio. For example, in the first stage, the selection ratio is 20; in the second stage, the selection ratios are 16, 12,8 and 4; . In the third stage, the selection ratio was 0.5.

In an embodiment, in order to achieve a better collimation effect of the microlens array, the structure of the microlens array can be limited to achieve a corresponding effect. Specifically, the center thickness of the microlens array of the preset shape is set to 30 to 40 micrometers, and the radius of curvature is set to 250 to 300 micrometers, whereby the divergence angle after collimation of the microlens array can be made smaller than 5 ° (full angle, 1/e) ² ). Through the dry etching process, different selection ratios are selected at different stages, and the flow of passivation gas is regulated, so that the microlens array with the preset shape can be finally obtained.

As an optional implementation manner of the embodiment of the invention, the micro lens array obtained by the preparation method of the micro lens array can be used at a light emitting window of a vertical cavity surface emitting laser. Thus, the preparation method of the microlens array can be integrated with the preparation process of the vertical cavity surface emitting laser. Specifically, before forming the microlens-shaped photoresist mask on the first surface of the substrate, the method further comprises: sequentially forming a first distributed feedback Bragg reflector, an active region and a second distributed feedback Bragg reflector on a second surface of the substrate, wherein the second surface is another surface which is arranged opposite to the first surface on the substrate; and processing the substrate to obtain the substrate with the preset thickness.

Specifically, before forming the photoresist mask on the first surface of the substrate, a structure of a VCSEL wafer, such as a first distributed feedback bragg reflector, an active region, and a second distributed feedback bragg reflector, may be formed on the second surface of the substrate, and then, bonding, thinning, polishing, and other processes are used to obtain a substrate with a specific thickness. The substrate may be a GaAs substrate. The structure of the VCSEL wafer may include the above structure, and may further include other structures, such as a buffer layer, etc. The embodiment of the invention does not limit the structure of the VCSEL wafer, and the VCSEL wafer can adopt any conventional VCSEL wafer structure.

Example 2

The embodiment of the invention provides a preparation method of a micro lens array, which is realized by adopting the following processes as shown in fig. 2 to 6: spin-coating photoresist positive photoresist 3 on the back of the thinned GaAs substrate 2 of the back-emitting VCSEL wafer 1, then pre-baking, wherein redundant solvent in the photoresist 3 film is driven away and exposed to ultraviolet light, the photodecomposition process of photoresist polymer is started, and the part 5 blocked by the photoetching plate 4 is protected for subsequent processes. After the ultraviolet exposure is completed, a photoresist mask 6 with a large area, a radius of curvature of about 150 micrometers and a center thickness of about 3 micrometers is formed through post baking, thermal reflux and other processes for a subsequent dry etching process.

Dry etching using RIE-ICP, using etching gas BCl in GaAs etching ₃ And Cl ₂ At the same time, adding a photoresist passivation gas CHF ₃ And N ₂ . In the etching process, the GaAs etching gas BCl is ensured ₃ And Cl ₂ Is constant by regulating the passivation gas CHF ₃ And N ₂ The selection ratio in the dry etching process is continuously adjusted within the range of 20 to 0.5. Whereby a multi-step etch can be employed in the dry etch.

Specifically, the first 1/3 of the total etching duration is the first stage, the etching selectivity at this stage is about 20, and the radius of curvature of the etched GaAs is smaller than the radius of curvature of the photoresist itself and is about 100um. The etching condition is BCl ₃ Is 20sccm, cl ₂ Is 2sccm, CHF ₃ Is 10sccm, N ₂ The flow rate of (2 sccm). The middle 1/3 of the total etching duration is the second stage, and the etching conditions in the second stage are divided into 4 steps, so that the reaction gas BCl is ensured ₃ With Cl ₂ Unchanged amount, CHF ₃ And N ₂ The gas flows of (1) were 10sccm and 10sccm, 5sccm and 10sccm, 2sccm and 5sccm, 2sccm and 7sccm, respectively, and the selection ratios were 16, 12,8,4, respectively. The final 1/3 of the total etching duration is the third stage, and the etching condition in this stage is BCl ₃ Is 20sccm, cl ₂ Is 2sccm, CHF ₃ Is 2sccm, N ₂ The flow rate of (2) was 10sccm, and the etching selectivity was 0.5. The radius of curvature of the etched microlens 7 is larger than that of the photoresist itself, about 300um, and the center thickness of the microlens is about 30um. The microlens array is adopted to collimate the light beams, and the divergence angle after collimation is smaller than 5 degrees (full angle, 1/e) ² )。

In this embodiment, the selection ratio of the dry etching is adjusted to be continuously varied in the range of 20 to 0.5 by adding a passivation gas. If the passivation gas is not added, only etching gas is adopted, and a fixed selection ratio is kept all the time in the whole etching process, the curvature radius Roc of the prepared micro-lens structure is smaller, and when the micro-lens structure is adopted for collimation, the divergence angle after collimation is 10 degrees (full angle, 1/e) ² ) About, a better collimation effect cannot be achieved.

Example 3

The embodiment of the invention provides a microlens array, which is prepared by adopting the preparation method of the microlens array in the

embodiment

1 or 2. The microlens array provided by the embodiment of the invention is prepared by adopting a dry etching process of adding passivation gas and step etching, so that the microlens has a good collimation effect, and is suitable for being applied to mass production of vertical cavity surface emitting lasers.

Example 3

The embodiment of the invention provides a vertical cavity surface emitting laser structure, which comprises: a substrate; the microlens array located on the first surface of the substrate is prepared by the preparation method of the microlens array described in the

above embodiment

1 or 2; the first distributed feedback Bragg reflector, the active region and the second distributed feedback Bragg reflector are sequentially arranged on the second surface of the substrate, and the second surface is the other surface of the substrate, which is opposite to the first surface. In particular, other structures of the VCSEL wafer, such as buffer layers, electrodes, etc., may also be included on the second surface of the substrate.

Although the exemplary embodiments and their advantages have been described in detail, those skilled in the art may make various changes, substitutions and alterations to these embodiments without departing from the spirit of the invention and the scope of protection as defined by the appended claims. For other examples, one of ordinary skill in the art will readily appreciate that the order of the process steps may be varied while remaining within the scope of the present invention.

Furthermore, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. From the present disclosure, it will be readily understood by those of ordinary skill in the art that processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present disclosure. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.

Claims

1. A method of manufacturing a microlens array, comprising:

forming a photoresist mask in a micro-lens shape on a first surface of a substrate, wherein the substrate is a GaAs substrate;

etching the photoresist mask and the substrate by adopting a dry etching process based on etching gas and passivation gas to form a microlens array with a preset shape on the substrate, ensuring that the flow of the etching gas is unchanged in the dry etching process, and adjusting the proportion of the passivation gas to gradually reduce the etching selection ratio value;

the passivation gas includes CHF ₃ And N ₂ The dry etching process comprises the following steps: three stages;

in the first stage of etching, a passivation gas CHF ₃ And N ₂ The flow ratio of (2) is 6:1-4:1;

in the second stage of etching, dry etching includes four steps, the first step of passivating gas CHF ₃ And N ₂ The flow ratio of (2) is 1:1, and the second step of passivation gas CHF ₃ And N ₂ The flow ratio of (2) is 1:2, and the passivation gas CHF is adopted in the third step ₃ And N ₂ The flow ratio of (2) to (5), the fourth passivation gas CHF ₃ And N ₂ The flow ratio of (2) to (7);

in the third stage of etching, the passivation gas CHF ₃ And N ₂ The flow ratio of (1) to (4) to (1) to (6);

before forming the microlens-shaped photoresist mask on the first surface of the substrate, the method further comprises:

sequentially forming a first distributed feedback Bragg reflector, an active region and a second distributed feedback Bragg reflector on a second surface of a substrate, wherein the second surface is another surface which is arranged opposite to the first surface on the substrate;

and processing the substrate to obtain the substrate with the preset thickness.

2. The method of manufacturing a microlens array according to claim 1, wherein the dry etching process includes: three stages;

in the first stage of etching, the etching selectivity ratio is more than 19 and less than 21;

in the second stage of etching, the ratio of etching selectivity is more than 2 and less than 18;

in the third stage of etching, the ratio of etching selectivity is more than 0.2 and less than 1.

3. The method of manufacturing a microlens array according to claim 2, wherein in the second stage of etching, dry etching includes four steps, the first step selection ratio is greater than 15 and less than 18, the second step selection ratio is greater than 11 and less than 14, the third step selection ratio is greater than 7 and less than 10, and the fourth step selection ratio is greater than 3 and less than 6.

4. The method of claim 1, wherein the pre-shaped microlens array has a center thickness of 30 to 40 microns and a radius of curvature of 250 to 300 microns.

5. The method of manufacturing a microlens array according to claim 1, wherein forming a microlens-shaped photoresist mask on the first surface of the substrate comprises:

spin-coating photoresist on the first surface of the substrate, and performing pre-baking;

placing a photoetching plate on the surface of photoresist far away from the substrate, exposing and developing the photoresist;

and performing post-baking and thermal reflux plasticity on the photoresist subjected to exposure and development to obtain the photoresist mask in the shape of the microlens.