A method for fabricating a silicon-based microsphere array

Abstract

The application relates to the technical field of aspherical surface array devices, and specifically discloses a preparation method and a heating device of a silicon-based small ball array, which comprises the following steps: firstly, a surface treatment agent is evaporated on the surface of a silicon-based substrate to make the contact angle of the surface in the range of 30-35 degrees; then, a series of operations such as spin coating, glue spreading and photoetching are carried out to obtain a progressive glue column structure with low center and high edge; for the formed glue column structure, a local gradient temperature change heating mode is used to carry out heat reflow processing, and the heating temperature is set to have a gradient rising distribution trend from the edge to the center, then heating is carried out to successfully convert the glue column into an array small ball; finally, the array small ball is taken to carry out ICP etching operation to obtain a silicon-based small ball array. The silicon-based small ball array prepared by the method has high uniformity, and the problems of poor uniformity of the silicon-based small ball array caused by factors such as uneven thickness in the glue spreading process and inconsistent rate in the ICP etching stage are solved.

Description

Technical Field

[0001] This application relates to the field of aspherical array device technology, and in particular to a method for fabricating silicon-based microsphere arrays and a heating device. Background Technology

[0002] As modern communication systems become increasingly miniaturized, lightweight, and integrated, the components that make up these module systems are also becoming increasingly miniaturized and arrayed. As a key component in communication module systems, aspherical arrays play an indispensable role in fields such as sensing, imaging, and light sources.

[0003] There are various methods for fabricating aspherical arrays, mainly including thermal reflow, microdroplet jetting, and micromold direct pressing. Among them, thermal reflow and dry etching processes have been widely used in actual production due to their advantage of being able to mass-produce aspherical arrays with high uniformity. This process involves several key steps such as coating, photolithography, development, and thermal reflow. First, photolithography is used to construct the target size of the photoresist pillars. Then, a hot plate is used to heat the pillars, causing them to melt at high temperatures, and then the surface tension of the liquid itself forms a spherical structure. However, at present, the thermal reflow process usually uses a hot plate heating method with uniform temperature. This traditional process has revealed a series of problems that urgently need to be solved in practice.

[0004] First, during the homogenization process for photoresist with a thickness greater than 20 μm, centrifugal force causes the photoresist to exhibit an uneven distribution on the wafer, being thinner at the center and thicker at the edges. This unevenness directly negatively impacts the uniformity of the photoresist spheres after thermal reflow, specifically manifesting as a larger radius of curvature (ROC) at the edges compared to the center. For example, in the invention patent CN115343788 A, although the method and system for fabricating microlenses by photoresist exposure and thermal reflow utilizes homogenization photolithography and can produce lenses of different apertures, it cannot effectively solve the problem of poor photoresist sphere uniformity. Second, during the photoresist sphere etching process, the uneven ion concentration distribution within the etching machine leads to a significantly higher etching rate in the central region compared to the edge region. This phenomenon further exacerbates the problem of a smaller radius of curvature for the microspheres in the central region, causing a significant deviation between the microlens processing effect and the pre-designed parameters, ultimately resulting in a severe negative impact on the optical performance of the microlens.

[0005] In summary, effectively solving the quality problems of glue balls caused by uneven coating and etching rates has become a key technical challenge that urgently needs to be overcome in the field of aspherical array fabrication. This is of vital practical significance for promoting technological progress and improving product performance in this field. Summary of the Invention

[0006] In view of this, the purpose of this application is to provide a method for preparing a silicon-based microsphere array and a heating device to solve the problem of poor uniformity of the silicon-based microsphere array caused by factors such as uneven thickness during the homogenization process and inconsistent etching rate during the ICP etching stage.

[0007] To achieve the above-mentioned technical objectives, this application provides a method for fabricating a silicon-based microsphere array, comprising the following steps:

[0008] Step S1, Substrate surface treatment: A surface treatment agent is vapor-deposited onto the surface of the silicon-based substrate to achieve a contact angle of 30~35° on the surface of the silicon-based substrate.

[0009] Step S2, Spin coating: A spin coating operation is performed with the center of the silicon substrate as the center and the edge as the circumference to form a film with a thickness that increases from the center to the edge;

[0010] Step S3, Photolithography and Development: The photolithography film is photolithographically ...

[0011] Step S4, Hot Reflow: Place the glue column on a circular heating device, and set the temperature of the circular heating device to increase gradually from the edge to the center. Then heat for a preset time to form an array of small balls from the glue column.

[0012] Step S5, ICP etching: Perform ICP etching on the array of microspheres for a preset etching time to obtain a silicon-based microsphere array.

[0013] Furthermore, based on the difference in etching rate between the center and edge of the array microspheres, the temperature difference of each region of the adhesive column during the thermal reflow stage is adjusted.

[0014] Furthermore, in step S5, when the etching rate decreases gradually from the center to the edge of the array spheres and the etching rate difference is 2.6%, in step S4, the adhesive column forms a gradient heating trend from the center to the edge and the temperature difference is set to 2%.

[0015] Furthermore, in step 4, the temperature difference between the center and the edge is 1~10 ℃.

[0016] Furthermore, in step S2, the thickness of the adhesive film, which increases from the center to the edge, is 23~24 μm; in step S3, the height of the adhesive column, which increases from the center to the edge, is 23~24 μm.

[0017] Furthermore, in the ICP etching step S5, the etching gas is one or more of SF6 and C4F8. Further, when the etching gas includes SF6 and C4F8, the gas flow rate of SF6 is 40 sccm and the gas flow rate of C4F8 is 60 sccm.

[0018] This application also provides a circular heating device for preparing silicon-based microsphere arrays, which is composed of a circular thermocouple and a plurality of annular thermocouples distributed along the circumference from the center, with annular partitions between the thermocouples.

[0019] Furthermore, the radius of the circular thermocouple is 50 mm; there are 3 annular thermocouples, and the annular thermocouples distributed along the circumference of the center have ring widths of 25, 25, and 50 mm, respectively.

[0020] Furthermore, the heating temperatures of the thermocouples distributed along the center to the circumference are set to 164 ℃, 165 ℃, 167 ℃, and 170 ℃ respectively.

[0021] In summary, this application provides a method for fabricating a silicon-based microsphere array, comprising the following steps: First, a surface treatment agent is deposited on the surface of a silicon-based substrate to bring the contact angle of the surface to within the range of 30-35°. Then, a series of operations, including homogenization and photolithography, are performed to obtain a columnar structure with a low center and high edge. For the formed columnar structure, a localized gradient temperature change heating method is used for thermal reflow treatment. Specifically, the localized gradient temperature change is set to a temperature distribution that increases gradually from the edge to the center. Heating for a preset time allows the columnar structure to successfully transform into an array of microspheres. Finally, the array of microspheres is subjected to ICP etching for a preset time to obtain the silicon-based microsphere array. The silicon-based microsphere array prepared using the method of this application exhibits high uniformity.

[0022] Compared to existing technologies, especially the uniform heating method used in traditional hot reflow of adhesive columns, this invention innovatively introduces a localized temperature-varying heating strategy to control the hot reflow molding process of the adhesive columns. Furthermore, by setting a temperature gradient process from the edge to the center during the localized temperature-varying heating process, the microspheres after hot reflow exhibit a trend of gradually increasing radius of curvature from the outside to the inside. This unique temperature distribution pattern effectively compensates for the poor consistency problem caused by the silicon substrate during the homogenization and ICP etching stages, thereby producing a silicon-based microsphere array with excellent uniformity. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in 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.

[0024] Figure 1 A process flow diagram for fabricating silicon-based microsphere arrays is provided for embodiments of this application;

[0025] Figure 2 Top view (left) and side view (right) of the circular heating device provided in the embodiments of this application;

[0026] Figure 3 This is a schematic diagram of the ICP etching operation on the array of microspheres provided in an embodiment of this application;

[0027] Figure 4 This is a diagram showing the test results of the radius of curvature of the silicon-based microsphere array provided in Embodiment 2 of this application;

[0028] Figure labels: 1. Array of microspheres; 2. Gel spheres formed during thermal reflow; 3. ICP etching. Detailed Implementation

[0029] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments in this application specification, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection claimed in this application.

[0030] The raw materials used in this invention are not particularly restricted in terms of their source; they can be purchased from the market or prepared using conventional methods known to those skilled in the art.

[0031] See Figure 1 This invention provides a method for fabricating a silicon-based microsphere array, comprising the following steps:

[0032] Step S1, Substrate surface treatment: A surface treatment agent is vapor-deposited onto the surface of the silicon-based substrate to achieve a contact angle of 30~35° on the surface of the silicon-based substrate.

[0033] Step S2, Spin coating: A spin coating operation is performed with the center of the silicon substrate as the center and the edge as the circumference to form a film with a thickness that increases from the center to the edge;

[0034] Step S3, Photolithography and Development: The photolithography film is photolithographically ...

[0035] Step S4, Hot Reflow: Place the glue column on a circular heating device, and set the temperature of the circular heating device to increase gradually from the edge to the center. Then heat for a preset time to form an array of small balls from the glue column.

[0036] Step S5, ICP etching: Perform ICP etching on the array of microspheres for a preset etching time to obtain a silicon-based microsphere array (e.g., Figure 3 (As shown).

[0037] It should be noted that the gradient temperature change heating method described above can generate a progressively smaller edge radius of curvature and a relatively larger center radius of curvature on the substrate surface. Due to the limitations of spin coating and ICP etching techniques, the spheres typically exhibit a progressive distribution pattern with a large edge radius of curvature and a small center radius of curvature. However, this invention cleverly utilizes this non-uniformity to counteract the sphere structure characteristics formed during the thermal reflow stage, thereby significantly improving the overall uniformity of the silicon-based spheres.

[0038] Preferably, the temperature difference between different regions of the adhesive column during the thermal reflow stage is adjusted based on the difference in etching rates between the center and edge of the array microspheres. In some embodiments, when the etching rate decreases gradually from the center to the edge of the array microspheres in step S5 and the etching rate difference is 2.6%, the adhesive column in step S4 forms a gradient heating trend from the center to the edge and the temperature difference is set to 2%.

[0039] It should be noted that this precise matching relationship between temperature and etching rate is to compensate for the non-uniformity in the ICP etching process. Due to the inherent limitations of ICP etching, the etching rate at the center is often greater than that at the edges. By setting a temperature gradient to control the change trend of the microsphere curvature radius after thermal reflow, the problem of poor lens consistency caused by the difference in etching rate is offset.

[0040] More preferably, the temperature difference between the center and the edge in step 4 is 1~10 °C.

[0041] In some embodiments, in step S2, the thickness of the adhesive film, which increases from the center to the edge, is 23~24 μm; in step S3, the height of the adhesive column, which increases from the center to the edge, is 23~24 μm.

[0042] It should be noted that during the photoresist homogenization process, the centrifugal force causes the photoresist to exhibit an uneven distribution on the wafer, with a thinner center and thicker edges; the photoresist pillars constructed from this photoresist film with thickness differences also exhibit an uneven state accordingly.

[0043] In some embodiments, during the ICP etching in step S5, the etching gas is one or more of SF6 and C4F8. Preferably, when the etching gas includes SF6 and C4F8, the gas flow rate of SF6 is 40 sccm and the gas flow rate of C4F8 is 60 sccm.

[0044] In some embodiments, the surface treatment agent is HDMS.

[0045] It should be noted that HDMS, as a surface treatment agent, can change the surface properties of silicon-based substrates and adjust parameters such as the contact angle and surface energy of the substrate surface, so that the photoresist can better adhere to the substrate surface and be more evenly distributed during the subsequent spin coating process.

[0046] This application provides a circular heating device for preparing a silicon-based microsphere array, which is composed of a circular thermocouple and multiple annular thermocouples distributed along the circumference from the center, with annular partitions between the thermocouples.

[0047] Specifically, the annular partition is made of Teflon.

[0048] It should be noted that the nesting of circular thermocouples and multiple annular thermocouples allows for independent monitoring and adjustment of the temperature in the center and different annular regions, thereby achieving gradient temperature control at the edges and center to meet the temperature distribution requirements during heat reflow. The annular baffles (such as those made of Teflon) serve to insulate and separate the temperatures of different regions, preventing disordered heat conduction between different thermocouple regions. This further improves the accuracy and stability of temperature control, ensuring the uniformity and stability of temperature distribution during heat reflow. This is beneficial for forming high-quality silicon-based array microspheres, thereby improving the uniformity and performance of the silicon-based microsphere array.

[0049] Preferably, the radius of the circular thermocouple is 50 mm; three annular thermocouples are provided, and the annular thermocouples distributed along the circumference of the center have ring widths of 25, 25, and 50 mm, respectively.

[0050] More preferably, the heating temperatures of the thermocouples distributed along the circumference from the center are set to 164 ℃, 165 ℃, 167 ℃, and 170 ℃ respectively.

[0051] The applicant further provides the following specific embodiments to describe the present invention. It should be noted that these embodiments are merely descriptive and do not limit the present invention in any way.

[0052] Example 1

[0053] See Figure 2 This invention provides a circular heating device for preparing a silicon-based microsphere array. The circular heating device has a radius of 150 mm and is composed of a circular thermocouple with a radius of 50 mm and three annular thermocouples with ring widths of 25, 25, and 50 mm, respectively, distributed along the circumference from the center. An annular partition made of Teflon is also provided between the thermocouples.

[0054] Example 2

[0055] See Figure 2This invention provides a method for fabricating a silicon-based microsphere array, comprising the following steps:

[0056] Step S1, Substrate treatment: Immerse the silicon substrate in acetone and sonicate for 6 minutes to clean it. Transfer the cleaned silicon substrate to the chamber of the vapor deposition equipment and adjust the temperature in the chamber to 130 ℃ and the pressure to 4600 Pa. Under these conditions, introduce HDMS into the chamber for vapor deposition for 5 minutes. At this time, the contact angle of the silicon substrate surface reaches 30~35°.

[0057] Step S2, Spin coating: Using a full-core micro automatic spin coating machine, AZ4562 photoresist is spin coated on the silicon substrate surface after step S1 at a speed of 1700 r / min. After two spin coatings, a film with a thickness of 23~24 μm is obtained.

[0058] Step S3, Photolithography Development: Photolithography is performed using a SUSS MA6 contact lithography machine and a photomask, with the exposure dose set to 1400 mJ / cm². 2 After photolithography, AZ300MIF developer was used for 20 min of development to obtain a photoresist column with a height of 23~24 μm.

[0059] Step S4, hot reflow: Place the photoresist column on the heating device prepared in Example 1, and set the temperature of the thermocouples from the inside to the outside to 164 ℃, 165 ℃, 167 ℃ and 170 ℃ respectively. Heat for 5 min to allow the photoresist to melt and form an array of small balls by relying on surface tension.

[0060] Step S5, ICP etching: Place the array microspheres in the reaction chamber of the ICP etching machine, set the gas flow rate of SF6 to 40 sccm, the gas flow rate of C4F8 to 60 sccm, the upper electrode power to 500 W, the chamber pressure to 4 mt, and the etching time to 50 min to obtain the silicon-based microsphere array.

[0061] Test 1, Uniformity test of surface radius: Eight points were randomly selected at the edge and center of the silicon-based microsphere array obtained in the above embodiment to test its surface radius. The test results are as follows. Figure 4 As shown.

[0062] right Figure 4 The data from 8 points were analyzed, and the radius of curvature fluctuated within a range of 1100±65μm. According to the calculation method of (Max-Min) / (Max+Min), its uniformity was 4.2%, which meets the shipping requirements.

[0063] The above are merely preferred embodiments of this application and are not intended to limit the present invention. Although this application has been described in detail with reference to examples, those skilled in the art can still modify the technical solutions described in the foregoing examples or make equivalent substitutions for some of the technical features. However, any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method of fabricating a silicon-based microsphere array, the method comprising: The method comprises the following steps: ​ Step S1, substrate surface treatment: evaporating a surface treatment agent on the surface of a silicon-based substrate to make the contact angle of the surface of the silicon-based substrate reach 30-35°; Step S2, uniform coating: performing spin coating operation with the center of the silicon-based substrate as the center and the edge as the circumference to form a glue film with thickness gradually increasing from the center to the edge; Step S3, photoetching and developing: performing photoetching on the glue film using a photoetching machine and a mask, and then developing to obtain glue columns with height gradually increasing from the center to the edge; Step S4, thermal reflow: placing the glue columns on a circular heating device, setting the temperature of the circular heating device to gradually increase from the edge to the center, and then heating for a preset time to form arrayed small balls; Step S5, ICP etching: performing ICP etching operation on the arrayed small balls for a preset time to obtain a silicon-based small ball array.

2. The method according to claim 1, wherein, in the step S5, the temperature difference of each region of the glue column in the thermal reflow stage is adjusted according to the etching rate difference between the center and the edge of the arrayed small balls.

3. The method according to claim 2, wherein, when the etching rate gradually decreases from the center to the edge of the arrayed small balls and the etching rate difference is 2.6%, the temperature of the glue column gradually increases from the center to the edge in the step S4, and the temperature difference is set to 2%. The temperature difference between the center and the edge in the step S4 is 1-10°C.

5. The method according to claim 1, wherein, in the step S2, the thickness of the glue film gradually increasing from the center to the edge is 23-24μm; and in the step S3, the height of the glue column gradually increasing from the center to the edge is 23-24μm.

4. The method of claim 3, wherein the silicon-based microsphere array is prepared by a method comprising:

6. The method according to claim 1, wherein, in the ICP etching of the step S5, the etching gas is one or more of SF6 and C4F8.

7. The method according to claim 6, wherein, when the etching gas comprises SF6 and C4F8, the gas flow of SF6 is 40sccm and the gas flow of C4F8 is 60sccm. The circular heating device is formed by embedding a circular thermocouple and a plurality of annular thermocouples distributed along the center to the circumference of the circular heating device, and annular partitions are arranged between the thermocouples. The radius of the circular thermocouple is 50mm; the annular thermocouples are 3 in number, and the ring widths of the annular thermocouples distributed along the center to the circumference are 25mm, 25mm and 50mm, respectively. The heating temperatures of the thermocouples distributed along the center to the circumference are set to 164°C, 165°C, 167°C and 170°C, respectively. ​ ​ 8. The method of claim 1, wherein the silicon-based microsphere array is prepared by a method comprising: ​ ​ 9. The method of claim 8, wherein the silicon-based microsphere array is prepared by a method comprising: ​ ​ 10. The method of claim 9, wherein the silicon-based microsphere array is prepared by a method comprising: ​ ​

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