Micro-lens hot reflow device and method with controllable atmosphere and flow field

Abstract

The application discloses a kind of micro-lens hot reflow devices with atmosphere and flow field synergic controllable, comprising: a multi-zone independent control heating platform;A closed atmosphere chamber surrounding the heating platform;A gas path system connected with the closed atmosphere chamber, for providing at least two controllable atmospheres into the cavity and accurately controlling its mixing ratio;An active airflow homogenization system arranged in the closed atmosphere chamber, located above the heating platform;A substrate located on the upper end surface of the heating platform;A temperature monitoring module for real-time monitoring of the two-dimensional temperature field distribution on the substrate surface;And an intelligent control system, the intelligent control system is respectively connected with the heating platform, gas path system, temperature monitoring module signal connection.It also discloses a kind of micro-lens hot reflow method with atmosphere and flow field synergic controllable.The application can effectively solve the problem of environmental interference, thermal mass transfer uneven and single regulation dimension.

Description

Technical Field

[0001] This invention belongs to the field of micro-nano optical device manufacturing and microfabrication technology, specifically a microlens thermal reflow device and method with controllable atmosphere and flow field. Background Technology

[0002] Although the microlens hot reflow method is simple in process, it is limited by the single function of traditional hot plates and faces three major technical bottlenecks:

[0003] 1. Environmental interference bottleneck: In open or semi-open heating environments, fluctuations in ambient humidity and oxygen content can uncontrollably alter the thermodynamic properties of photoresist (such as glass transition temperature Tg and surface energy), resulting in poor batch-to-batch repeatability (>10% morphology deviation).

[0004] 2. Bottleneck of uneven heat / mass transfer: Traditional hot plates only provide bottom heating. For large-sized or warped substrates, uneven heat flow distribution leads to inconsistent radii of curvature between the center and edges of the microlens array. Simultaneously, the lack of optimization of the reaction atmosphere flow field results in localized concentration differences.

[0005] 3. Limited process control: The morphology of microlenses can only be controlled to a limited extent by the size and temperature profile of the initial photoresist pillars. There is a lack of effective in-situ control methods, making it difficult to fabricate complex aspherical or irregularly shaped lenses.

[0006] To address these issues, existing technologies, such as CN201910123456.0, propose a vacuum thermal reflow apparatus. While this isolates the area from air interference, it cannot introduce a functional atmosphere, and the vacuum environment may accelerate the evaporation of photoresist solvents, leading to surface defects. Another paper (J. Micromech. Microeng., 2020, 30, 055001) reports a method using organic solvent vapor annealing; however, this process is carried out in a simple, closed container, making it difficult to precisely control the vapor concentration and temperature uniformity, resulting in significant challenges in reproducibility.

[0007] In summary, existing technical solutions either oppose atmosphere control and temperature control (such as vacuum solutions) or simply superimpose them (such as solvent vapor containers), failing to achieve dynamic decoupling and coordinated precise control of multiple physical fields such as temperature field, atmosphere composition, and flow field distribution.

[0008] Existing technologies cannot simultaneously achieve high repeatability, high uniformity, and programmable morphology in the fabrication of microlenses. Therefore, a microlens thermal reflow device and method with controllable atmosphere and flow field are provided. Summary of the Invention

[0009] To address the aforementioned problems in the prior art, this invention provides a microlens heat recirculation device and method with controllable atmosphere and flow field, which can achieve dynamic decoupling and precise control of the temperature field, reaction atmosphere composition, and distribution flow field within the reaction chamber, thereby effectively solving the problems of environmental interference, uneven heat and mass transfer, and single control dimension.

[0010] The technical solution to achieve the above objectives is:

[0011] One of the present inventions provides a microlens thermal reflow device with synergistic controllable atmosphere and flow field, comprising:

[0012] A multi-zone independently controlled heating platform;

[0013] A sealed atmosphere chamber surrounding the heating platform;

[0014] A gas path system connected to the sealed atmosphere chamber for supplying at least two controllable atmospheres into the chamber and precisely controlling their mixing ratio;

[0015] An active airflow homogenization system is disposed within the sealed atmosphere chamber and above the heating platform;

[0016] A substrate located on the upper surface of the heating platform;

[0017] A temperature monitoring module for real-time monitoring of the two-dimensional temperature field distribution on the substrate surface;

[0018] And an intelligent control system, which is connected to the heating platform, the gas path system and the temperature monitoring module respectively.

[0019] Preferably, the heating platform adopts an embedded multi-zone heater based on high-temperature co-fired ceramic technology, and each heating zone is controlled by an independent PID module.

[0020] Preferably, the sealed atmosphere chamber adopts a double-layer structure, with the inner layer being chemically resistant quartz glass and the outer layer being a stainless steel water-cooled jacket. The chamber body is provided with a main air inlet, an auxiliary air inlet for mixing different gases, and a multi-hole outlet arranged in a ring.

[0021] Preferably, the gas path system includes at least two gas mass flow controllers for precisely controlling the mixing ratio of two or more gases.

[0022] Preferably, the active airflow homogenization system is composed of a microporous flow equalizer and a flow guiding cavity;

[0023] in,

[0024] The flow guiding cavity is located above the microporous flow equalizer. Its conical design transforms the intake airflow from a point source to a surface source, and then it is homogenized twice by the microporous flow equalizer to form a uniform and stable laminar flow atmosphere above the substrate.

[0025] Preferably, the temperature monitoring module combines a high-precision infrared thermal imager with multiple fixed-point infrared sensors to monitor and provide feedback on the two-dimensional temperature field distribution on the substrate surface in real time.

[0026] Preferably, the intelligent control system is used to receive temperature, gas flow and pressure sensor signals in real time, and dynamically adjust the power of each heating zone of the heating platform and the gas mass flow controller to compensate for thermal disturbances caused by airflow and perform independent control of temperature and atmosphere.

[0027] The pressure sensor is used to monitor and provide feedback on the air pressure inside the sealed atmosphere chamber in real time.

[0028] A second aspect of the present invention provides a microlens thermal reflow method with synergistic controllable atmosphere and flow field, comprising:

[0029] Step S1: Place the substrate with the photoresist pattern on the heating platform;

[0030] Step S2: Close the sealed atmosphere chamber and purge it with inert gas;

[0031] Step S3: Introduce a mixed atmosphere of vapor containing organic solvent and inert gas into the sealed atmosphere chamber.

[0032] Step S4: Start the heating platform and execute the heat reflux temperature curve according to the preset program. At the same time, the intelligent control system introduces a predetermined proportion of functional gas into the cavity to maintain the coordinated stability of atmosphere and temperature.

[0033] Step S5: The partial pressure of the organic solvent vapor is dynamically adjusted by the intelligent control system to regulate the radius of curvature and focal length of the obtained microlens.

[0034] Step S6: After reflux, the sample is cooled using a preset cooling rate and then removed.

[0035] Preferably, in step S2, the purging process includes a preheating stage at 50-80°C.

[0036] Preferably, in step S3, the organic solvent vapor is one of isopropanol, acetone or ethyl acetate, and its partial pressure is adjustable in the range of 10%-80%.

[0037] Compared with the prior art, the beneficial effects of the present invention are:

[0038] This invention, through a fully enclosed microenvironment and pretreatment process, greatly suppresses environmental fluctuation interference, reducing the batch-to-batch repeatability error of key dimensions of microlenses from >10% to <2%.

[0039] The active airflow homogenization and multi-zone temperature control technology in this invention ensure that the curvature radius non-uniformity of the microlens array fabricated on a 4-inch substrate is <±1.5%, which is far superior to traditional processes.

[0040] This invention elevates the atmosphere composition from a "protective" variable to a "functional" variable, providing an effective means for in-situ programmed control of the optical properties of microlenses (such as focal length and aberrations), and is particularly suitable for the fabrication of complex devices such as aspherical microlenses;

[0041] This invention exhibits good compatibility with different types of positive / negative photoresists, SU-8, as well as glass substrates, silicon substrates, flexible polymer substrates, etc.

[0042] In summary, this invention achieves high repeatability (batch-to-batch error <2%), high uniformity (non-uniformity <±1.5%), and programmable fabrication of microlenses, solving the problems of environmental sensitivity, poor uniformity, and limited control dimensions in traditional processes. Attached Figure Description

[0043] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0044] Figure 1 This is a schematic diagram of a microlens thermal reflux device with controllable atmosphere and flow field according to the present invention;

[0045] Figure 2 This is a flowchart of a microlens thermal reflow method with synergistic control of atmosphere and flow field according to the present invention;

[0046] Figure 3 This is a comparison of the cross-sectional morphology of the microlens arrays prepared by the conventional device and the device described in Embodiment 1 of the present invention;

[0047] Figure 4 This is the curve showing the change in the radius of curvature of the microlenses prepared under different isopropanol (IPA) vapor partial pressures in Example 2 of this invention. Detailed Implementation

[0048] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0049] like Figure 1 As shown, a microlens thermal reflux device with controllable atmosphere and flow field is characterized by comprising:

[0050] A multi-zone independently controlled heating platform 1.

[0051] In this embodiment, the heating platform 1 adopts an embedded multi-zone heater 1a based on high-temperature co-fired ceramic technology. Each heating zone is controlled by an independent PID module to ensure that the temperature uniformity within the working area (150mm×150mm) is ≤±0.5℃.

[0052] A sealed atmosphere chamber 2 surrounding the heating platform 1.

[0053] In this embodiment, the sealed atmosphere chamber 2 adopts a double-layer structure, with the inner layer being chemically resistant quartz glass and the outer layer being a stainless steel water-cooled jacket. This design not only facilitates observation but also allows for precise control of the chamber wall temperature, preventing vapor from condensing at the top and ensuring the stability of the atmosphere composition. The chamber body is provided with a main air inlet 3, an auxiliary air inlet 3a for mixing different gases, and a multi-hole outlet 4 arranged in a ring, laying the structural foundation for the uniformity of the flow field.

[0054] A gas path system connected to a sealed atmosphere chamber 2 for supplying at least two controllable atmospheres into the chamber and precisely controlling their mixing ratio.

[0055] In this embodiment, the gas path system includes at least two gas mass flow controllers for precisely controlling the mixing ratio of two or more gases.

[0056] An active airflow homogenization system is installed in a sealed atmosphere chamber 2 and located above the heating platform 1.

[0057] In this embodiment, the active airflow homogenization system is composed of a microporous flow equalizer 5 and a flow guiding cavity 8.

[0058] in,

[0059] The flow guiding cavity 8 is located above the microporous flow equalizer 5. Its conical design transforms the intake airflow from a point source to a surface source. Then, it is homogenized twice by the microporous flow equalizer 5 (pore diameter 100-500μm, porosity 40%-60%), forming a uniform and stable laminar flow atmosphere above the substrate 9.

[0060] A substrate 9 located on the upper surface of the heating platform 1.

[0061] A temperature monitoring module 6 for real-time monitoring of the two-dimensional temperature field distribution on the surface of substrate 9.

[0062] In this embodiment, the temperature monitoring module 6 uses a combination of a high-precision infrared thermal imager 6a and multiple fixed-point infrared sensors 6b to monitor and provide feedback on the two-dimensional temperature field distribution on the substrate surface in real time.

[0063] And an intelligent control system 7, which is connected to the heating platform 1, the gas system and the temperature monitoring module 6 respectively.

[0064] In this embodiment, the intelligent control system 7 is used to receive temperature, gas flow and pressure sensor signals in real time, and dynamically adjust the power of each heating zone of the heating platform 1 and the gas mass flow controller to compensate for thermal disturbances caused by airflow and to perform independent control of temperature and atmosphere.

[0065] The pressure sensor is used to monitor and provide feedback on the air pressure inside the sealed atmosphere chamber 2 in real time.

[0066] like Figure 1 , 2 As shown, a microlens thermal reflux method with synergistic control of atmosphere and flow field includes:

[0067] Step S1: Place the substrate with the photoresist pattern on the heating platform 1.

[0068] Step S2: Close the sealed atmosphere chamber 2 and purge it with inert gas.

[0069] In the embodiment, the purging process includes a low-temperature preheating stage of 50-80°C.

[0070] Step S3: Introduce a mixed atmosphere of vapor containing organic solvent and inert gas into the sealed atmosphere chamber 2.

[0071] In the examples, the organic solvent vapor is one of isopropanol, acetone or ethyl acetate, and its partial pressure is adjustable in the range of 10%-80%.

[0072] Step S4: Start the heating platform 1 and execute the heat reflux temperature curve according to the preset program. At the same time, the intelligent control system 7 introduces a predetermined proportion of functional gas (such as N2 / IPA mixed vapor) into the cavity to maintain the coordinated stability of atmosphere and temperature.

[0073] Step S5 involves dynamically adjusting the partial pressure of the organic solvent vapor through the intelligent control system 7 to regulate the radius of curvature and focal length of the resulting microlens. In other words, by actively controlling the partial pressure of the organic vapor, the surface tension and contact angle of the molten photoresist can be continuously and in situ regulated. This allows for 'programmable' precise control of the radius of curvature and focal length of the microlens without altering the initial pattern and chemical composition of the photoresist. This provides unprecedented flexibility for fabricating microlenses with specific optical properties (such as aspherical lenses).

[0074] Step S6: After reflux, the sample is cooled using a preset cooling rate and then removed. The preset cooling rate (such as step cooling) combined with the atmospheric environment effectively reduces thermal stress and prevents the microlens from cracking or developing internal stress.

[0075] Example 1: Verifying the effect of this device in improving uniformity

[0076] Conditions: A cylindrical photoresist (AZ 4620) array with a diameter of 50 μm and a center-to-center distance of 20 μm is fabricated on a 4-inch silicon substrate.

[0077] Control group: Using a conventional hot plate, refluxed at 160°C for 5 minutes in an air environment.

[0078] Experimental group: Using the device of this invention, the same temperature curve was used under a N2 atmosphere.

[0079] Result: As Figure 3 As shown, in arrays fabricated using conventional processes, the radius of curvature of the edge lenses is approximately 12% smaller than that of the center. In contrast, the array fabricated using the device of this invention exhibits a uniformity of lens curvature radius across the entire wafer of less than ±1.5%, fully demonstrating its superior uniformity control capability.

[0080] Example 2: Verifying the ability of atmosphere to control morphology

[0081] Conditions: Fix the photoresist pattern and temperature profile (160℃, 5min), and adjust the partial pressure of IPA vapor in N2 carrier gas (0% to 70%) using MFC.

[0082] Result: As Figure 4 As shown, as the IPA partial voltage increases from 0% to 70%, the contact angle of the microlens continuously decreases from 115° to 85°, while the corresponding radius of curvature increases significantly. This demonstrates that microlenses with different focal lengths can be fabricated on the same photoresist pattern by simply adjusting the atmosphere formulation, providing great flexibility for optical design.

[0083] Finally, it should be noted that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A microlens thermal reflux device with controllable atmosphere and flow field, characterized in that, include: A multi-zone independently controlled heating platform (1); A sealed atmosphere chamber (2) surrounding the heating platform (1); A gas path system connected to the sealed atmosphere chamber (2) for providing a mixed atmosphere of vapor containing organic solvent and inert gas into the chamber and for precisely controlling the mixing ratio therein; An active airflow homogenization system is installed inside the sealed atmosphere chamber (2) and above the heating platform (1); A pressure sensor for monitoring the air pressure inside the sealed atmosphere chamber (2); A substrate (9) located on the upper surface of the heating platform (1); A temperature monitoring module (6) for real-time monitoring of the two-dimensional temperature field distribution on the surface of the substrate (9); And an intelligent control system (7), which is connected to the heating platform (1), the gas system and the temperature monitoring module (6) respectively; The sealed atmosphere chamber (2) adopts a double-layer structure. The inner layer is chemically resistant quartz glass, and the outer layer is a stainless steel water-cooled jacket. The chamber body is provided with a main air inlet (3), an auxiliary air inlet (3a) for mixing different gases, and a multi-hole outlet (4) arranged in a ring. The gas path system includes at least two gas mass flow controllers for precisely controlling the mixing ratio of two mixed atmospheres, namely, vapor containing organic solvent and inert gas, or the mixing ratio of two or more gases. The active airflow homogenization system is composed of a microporous flow equalization plate (5) and a flow guiding cavity (8); The flow guide cavity (8) is located above the microporous flow equalizer (5). Its conical design transforms the intake airflow from a point source to a surface source, and then it is homogenized twice by the microporous flow equalizer (5) to form a uniform and stable laminar flow atmosphere above the substrate (9). The intelligent control system (7) is used to receive temperature, gas flow and pressure sensor signals in real time, and dynamically adjust the power of each heating zone of the heating platform (1) and the gas mass flow controller to compensate for the thermal disturbance caused by the airflow and to perform independent control of temperature and atmosphere. The pressure sensor is used to monitor and provide feedback on the air pressure inside the sealed atmosphere chamber (2) in real time.

2. The microlens heat reflow device with controllable atmosphere and flow field according to claim 1, characterized in that, The heating platform (1) adopts an embedded multi-zone heater (1a) based on high-temperature co-fired ceramic technology, and each heating zone is controlled by an independent PID module.

3. The microlens heat reflow device with controllable atmosphere and flow field according to claim 1, characterized in that, The temperature monitoring module (6) combines a high-precision infrared thermal imager (6a) with multiple fixed-point infrared sensors (6b) to monitor and provide feedback on the two-dimensional temperature field distribution on the substrate surface in real time.

4. A microlens thermal reflow method based on the microlens thermal reflow device with controllable atmosphere and flow field as described in claim 1, characterized in that, include: Step S1: Place the substrate with the photoresist pattern on the heating platform (1); Step S2: Close the sealed atmosphere chamber (2) and purge with inert gas; Step S3: Introduce a mixed atmosphere of vapor containing organic solvent and inert gas into the sealed atmosphere chamber (2); Step S4: Start the heating platform (1), execute the heat reflux temperature curve according to the preset program, and at the same time, introduce a predetermined proportion of functional gas into the cavity through the intelligent control system (7) to maintain the coordinated stability of atmosphere and temperature. Step S5: The partial pressure of the organic solvent vapor is dynamically adjusted by the intelligent control system (7) to regulate the radius of curvature and focal length of the obtained microlens. Step S6: After reflux, the sample is cooled using a preset cooling rate and then removed.

5. The microlens thermal reflow method according to claim 4, characterized in that, In step S2, the purging process includes a preheating stage at 50-80°C.

6. The microlens thermal reflow method according to claim 4, characterized in that, In step S3, the organic solvent vapor is one of isopropanol, acetone or ethyl acetate, and its partial pressure is adjustable in the range of 10%-80%.

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