Preparation method of silicon-based pellet array and heating device

Abstract

The invention relates to the technical field of aspheric array devices, and particularly discloses a preparation method of a silicon-based small ball array and a heating device.The preparation method comprises the following steps that firstly, a surface treating agent is evaporated on the surface of a silicon-based base material, so that the contact angle of the surface of the silicon-based base material is within the interval range of 30-35 degrees; then carrying out a series of operations of spin-coating and spin-coating glue and photoetching development to obtain a progressive glue column structure with a low center and a high edge; aiming at the formed rubber column structure, carrying out hot reflux treatment by applying a local gradient temperature change heating mode, setting a distribution trend that the heating temperature is increased in a gradient manner from the edge to the center, and then heating to successfully convert the rubber column into array small balls; and finally, performing ICP (Inductively Coupled Plasma) etching operation on the array small balls to obtain the silicon-based small ball array. The silicon-based small ball array prepared by the method shows relatively high uniformity, and the problem of poor uniformity of the silicon-based small ball array caused by factors such as non-uniform thickness in a glue uniformizing process and inconsistent rate in an ICP etching stage is solved.

Description

Technical Field

[0001] The present application relates to the technical field of aspheric array devices, and in particular to a preparation method and a heating device for a silicon-based small ball array. Background Art

[0002] As modern communication systems are becoming increasingly miniaturized, lightweight, and integrated, the components that make up the module system are also becoming increasingly miniaturized and arrayed. As a key component in the communication module system, the non-spherical array plays an indispensable role in the fields of sensing, imaging, and light sources.

[0003] There are various methods for preparing aspheric arrays, mainly covering thermal reflow, droplet injection and micro-mold direct pressing. Among them, thermal reflow and dry etching processes have been widely used in actual production due to their advantages of being able to mass-produce aspheric arrays with high uniformity. The process involves several key steps such as glue spreading, photolithography, development and thermal reflow. First, a glue column of the target size is constructed with the help of a photolithography process, and then a hot plate is used for heating, causing the glue column to melt in a high temperature environment, and then a spherical structure is formed by the surface tension of the liquid itself. However, at this stage, the thermal reflow process usually uses a hot plate heating method with uniform temperature. This traditional process has exposed a series of problems that need to be solved in practice.

[0004] First, when performing a photoresist coating operation with a thickness greater than 20 μm, the photoresist will be unevenly distributed on the wafer, with the center being thin and the edge being thick, due to the influence of centrifugal force. This unevenness will directly have a negative impact on the uniformity of the glue balls after thermal reflow, that is, the radius of curvature (ROC) of the edge glue balls is greater than that of the center glue balls. For example, in the method and system for making microlenses by photoresist exposure and heating reflow in the invention patent CN115343788 A, although the coating lithography process is used and lenses of different calibers can be made, the problem of poor uniformity of the glue balls cannot be effectively solved. Second, during the etching process of the glue balls, the etching rate in the central area is significantly greater than that in the edge area due to the uneven distribution of ion concentration inside the etcher. This phenomenon further exacerbates the problem of the small radius of curvature of the small balls in the central area, causing the processing effect of the microlens to deviate greatly from the pre-designed parameters, and ultimately causing a serious negative impact on the optical performance of the microlens.

[0005] In summary, how to effectively solve the quality problem of glue balls caused by uneven glue distribution and etching rate has become a key technical problem that needs to be overcome in the current field of aspheric array preparation. It has 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 the present application is to provide a method for preparing a silicon-based small ball array and a heating device, which is used to solve the problem of poor uniformity of the silicon-based small ball array caused by factors such as uneven thickness during the coating process and inconsistent rate during the ICP etching stage.

[0007] In order to achieve the above technical objectives, the present application provides a method for preparing a silicon-based microsphere array, comprising the following steps:

[0008] Step S1, substrate surface treatment: evaporating a surface treatment agent on the surface of the silicon-based substrate so that the contact angle of the silicon-based substrate surface reaches 30-35°;

[0009] Step S2, coating: spin coating is performed with the center of the silicon-based substrate as the center and the edge as the circumference to form a coating film with a thickness increasing from the center to the edge;

[0010] Step S3, photolithography and development: using a photolithography machine and a mask to perform photolithography on the film, and after the photolithography is completed, performing a development operation to obtain a resin column with a height increasing from the center to the edge;

[0011] Step S4, thermal reflow: placing the glue column on a circular heating device, setting the temperature of the circular heating device to increase in a gradient from the edge to the center, and then heating for a preset time to form an array of small balls of the glue column;

[0012] Step S5, ICP etching: performing ICP etching operation on the array beads for a preset etching time to obtain a silicon-based bead array.

[0013] Furthermore, the temperature difference of each area of ​​the glue column in the thermal reflow stage is adjusted according to the difference in etching rate between the center and the edge of the array ball.

[0014] Furthermore, in step S5, when the etching rate decreases gradually from the center to the edge of the array ball and the etching rate difference is 2.6%, in step S4, the temperature of the glue column increases gradually from the center to the edge and the temperature difference is set to 2%.

[0015] Furthermore, the temperature difference between the center and the edge in step 4 is 1-10°C.

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

[0017] Further, in the ICP etching of 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] The present application also provides a circular heating device for preparing a silicon-based ball array, which is composed of a circular thermocouple and a plurality of annular thermocouples distributed from the center of the circle to the circumference, and an annular partition is provided between the thermocouples.

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

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

[0021] In summary, the present application provides a method for preparing a silicon-based small ball array, comprising the following steps: first, evaporating a surface treatment agent on the surface of a silicon-based substrate so that the contact angle of the surface is within the range of 30 to 35 °, then performing a series of operations such as uniform coating and photolithography and development to obtain a glue column structure with a low center and high edges; for the formed glue column structure, a local gradient temperature change heating method is used to carry out a heat reflow treatment, and in this process, the local gradient temperature change is specifically set to a distribution trend in which the temperature rises from the edge to the center in a gradient manner, and the heating is preset for a preset time to successfully transform the glue column into an array of small balls; finally, the array of small balls is subjected to ICP etching for a preset etching time to obtain a silicon-based small ball array. The silicon-based small ball array prepared by the method of the present application exhibits a high uniformity.

[0022] Compared with the prior art, especially the uniform heating method used in the traditional glue column heat reflow, the present invention innovatively introduces a local temperature change heating strategy to regulate the heat reflow molding process of the glue column, and in the heating process of the local temperature change, by setting a temperature change process with a gradient increase from the edge to the center, the small balls after heat reflow show a trend of gradually increasing curvature radius from the outside to the inside. This unique temperature distribution mode effectively compensates for the poor consistency problem caused by the silicon-based substrate in the glue-spinning and ICP etching stages, and then prepares a silicon-based small ball array with good uniformity. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present application or the technical solutions in 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 creative labor.

[0024] Figure 1 A process flow chart for preparing a silicon-based ball array provided in an embodiment of the present application;

[0025] Figure 2 A top view (left) and a side view (right) of a circular heating device provided in an embodiment of the present application;

[0026] Figure 3 A schematic diagram of the operation of performing ICP etching on array beads provided in an embodiment of the present application;

[0027] Figure 4 This is a test result diagram of the curvature radius of the silicon-based ball array provided in Example 2 of the present application;

[0028] Figure numerals: 1. Array balls; 2. Glue balls formed during thermal reflow; 3. ICP etching. DETAILED DESCRIPTION

[0029] The technical solutions of the embodiments of the present application will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the specification of the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection requested by the present application.

[0030] The sources of all raw materials in the present invention are not particularly limited and can be purchased from the market or prepared according to conventional methods known to those skilled in the art.

[0031] See also Figure 1 The present invention provides a method for preparing a silicon-based ball array, comprising the following steps:

[0032] Step S1, substrate surface treatment: evaporating a surface treatment agent on the surface of the silicon-based substrate so that the contact angle of the silicon-based substrate surface reaches 30-35°;

[0033] Step S2, coating: spin coating is performed with the center of the silicon-based substrate as the center and the edge as the circumference to form a coating film with a thickness increasing from the center to the edge;

[0034] Step S3, photolithography and development: using a photolithography machine and a mask to perform photolithography on the film, and after the photolithography is completed, performing a development operation to obtain a resin column with a height increasing from the center to the edge;

[0035] Step S4, thermal reflow: placing the glue column on a circular heating device, setting the temperature of the circular heating device to increase in a gradient from the edge to the center, and then heating for a preset time to form an array of small balls of the glue column;

[0036] Step S5, ICP etching: ICP etching is performed on the array beads for a preset etching time to obtain a silicon-based bead array (such as Figure 3 as shown).

[0037] It should be noted that, through the above-mentioned heating method of implementing gradient temperature change, a progressive colloidal ball structure with a relatively small edge curvature radius and a relatively large center curvature radius can be generated on the surface of the substrate. In view of the limitations of the spin coating process and ICP etching technology, the colloidal balls usually have a progressive distribution pattern with a large edge curvature radius and a small center curvature radius. However, the present invention cleverly utilizes this uneven characteristic to offset the ball structure characteristics formed in the thermal reflow stage, thereby significantly improving the overall consistency level of the silicon-based balls.

[0038] Preferably, the temperature difference of each area of ​​the glue column in the thermal reflow stage is adjusted according to the difference in etching rate between the center and the edge of the array ball. In some embodiments, when the etching rate in step S5 decreases gradually from the center to the edge of the array ball and the etching rate difference is 2.6%, the glue column in step S4 forms a gradient temperature increase 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 principle limitation of ICP etching itself, the etching rate at the center is often greater than that at the edge. By setting the temperature gradient to control the change trend of the curvature radius of the ball after thermal reflow, the problem of poor lens consistency caused by the difference in etching rate can be 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 increasing from the center to the edge is 23-24 μm; in step S3, the height of the adhesive column increasing from the center to the edge is 23-24 μm.

[0042] It should be noted that when the photoresist is being spread evenly, the photoresist is unevenly distributed on the wafer, with the center being thin and the edges being thick, due to the influence of centrifugal force; the photoresist column constructed by the photoresist film with different thicknesses also exhibits an uneven state accordingly.

[0043] In some embodiments, in the ICP etching of 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, adjust the contact angle, surface energy and other parameters of the substrate surface, so that the photoresist can better adhere to the substrate surface and be more evenly distributed in the subsequent coating process.

[0046] An embodiment of the present application provides a circular heating device for preparing a silicon-based ball array, which is composed of a circular thermocouple and a plurality of annular thermocouples distributed from the center of the circle to the circumference, and an annular partition is provided between the thermocouples.

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

[0048] It should be noted that the nesting of circular thermocouples and multiple annular thermocouples can independently monitor and adjust the temperature of the center and different annular areas, thereby achieving gradient control of the temperature of the edge and the center, and meeting the requirements for temperature distribution during the heat reflow process. The setting of annular partitions (such as Teflon materials) can play a role in heat insulation and separation of temperatures in different areas, prevent disordered heat conduction between different thermocouple areas, further improve the accuracy and stability of temperature control, ensure the uniformity and stability of temperature distribution during the heat reflow process, and facilitate the formation of high-quality silicon-based array beads, thereby improving the uniformity and performance of silicon-based bead arrays.

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

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

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

[0052] Example 1

[0053] See also Figure 2 An embodiment of the present invention provides a circular heating device for preparing a silicon-based ball 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 distributed along the center of the circle to the circumference and with ring widths of 25, 25, and 50 mm respectively. An annular partition made of Teflon is also provided between the thermocouples.

[0054] Example 2

[0055] See also Figure 2The present invention provides a method for preparing a silicon-based ball array, comprising the following steps:

[0056] Step S1, substrate treatment: immerse the silicon-based substrate in acetone for 6 minutes for ultrasonic cleaning, transfer the cleaned silicon-based substrate to the chamber of the evaporation equipment, and adjust the temperature in the chamber to 130 ° C and the pressure to 4600 Pa. Under this condition, HDMS is introduced into the chamber for evaporation. The evaporation time is 5 minutes, and the contact angle of the silicon-based substrate surface reaches 30-35°;

[0057] Step S2, coating: using a Quanxinwei automatic coating machine to spin-coat AZ4562 photoresist on the surface of the silicon-based substrate treated in step S1 at a speed of 1700 r / min, and obtaining a coating film with a thickness of 23-24 μm after two coatings;

[0058] Step S3, photolithography development: Use SUSS MA6 contact photolithography machine and mask for photolithography, and set the exposure dose to 1400 mJ / cm 2 After the photolithography, the AZ300MIF developer was used for 20 min to obtain a gel column with a height of 23-24 μm.

[0059] Step S4, thermal reflux: placing the resin column on the heating device prepared in Example 1, setting the temperature of the thermocouples from the inside to the outside to 164°C, 165°C, 167°C, and 170°C, heating for 5 minutes, so that the photoresist is in a molten state and forms array beads by surface tension;

[0060] Step S5, ICP etching: Place the array beads in the reaction chamber of the ICP etcher, set the gas flow rate of etching gas 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 a silicon-based bead array.

[0061] Test 1, surface radius uniformity test: 8 points were randomly selected at the edge and center of the silicon-based ball array obtained in the above embodiment, and the surface radius was tested. The test results are as follows: Figure 4 shown.

[0062] right Figure 4 The data of 8 points in the test are analyzed and the fluctuation range of the curvature radius is 1100±65μm. According to the calculation method of (Max-Min) / (Max+Min), the uniformity is 4.2%, which meets the shipment requirements.

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

Claims

1. A method for preparing a silicon-based ball array, characterized in that: The following steps are involved: Step S1, substrate surface treatment: evaporating a surface treatment agent on the surface of the silicon-based substrate so that the contact angle of the silicon-based substrate surface reaches 30-35°; Step S2, coating: spin coating is performed with the center of the silicon-based substrate as the center and the edge as the circumference to form a coating film with a thickness increasing from the center to the edge; Step S3, photolithography and development: using a photolithography machine and a mask to perform photolithography on the film, and after the photolithography is completed, performing a development operation to obtain a resin column with a height increasing from the center to the edge; Step S4, thermal reflow: placing the glue column on a circular heating device, setting the temperature of the circular heating device to increase in a gradient from the edge to the center, and then heating for a preset time to form an array of small balls of the glue column; Step S5, ICP etching: performing ICP etching operation on the array beads for a preset etching time to obtain a silicon-based bead array.

2. The method for preparing a silicon-based microsphere array according to claim 1, characterized in that: In the step S5, the temperature difference of each area of ​​the glue column in the thermal reflow stage is adjusted according to the difference in etching rate between the center and the edge of the array ball.

3. The method for preparing a silicon-based microsphere array according to claim 2, characterized in that: When the etching rate decreases gradually from the center to the edge of the array ball and the etching rate difference is 2.6%, in step S4, the temperature of the glue column increases gradually from the center to the edge and the temperature difference is set to 2%.

4. The method for preparing a silicon-based microsphere array according to claim 3, characterized in that: The temperature difference between the center and the edge in step 4 is 1-10°C.

5. The method for preparing a silicon-based microsphere array according to claim 1, characterized in that: In the step S2, the thickness of the adhesive film increasing from the center to the edge is 23-24 μm; in the step S3, the height of the adhesive column increasing from the center to the edge is 23-24 μm.

6. The method for preparing a silicon-based microsphere array according to claim 1, characterized in that: In the ICP etching of step S5, the etching gas is one or more of SF6 and C4F8.

7. The method for preparing a silicon-based microsphere array according to claim 6, characterized in that: 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.

8. A circular heating device in the method for preparing a silicon-based ball array according to any one of claims 1 to 7, characterized in that: The invention is formed by nesting a circular thermocouple and a plurality of annular thermocouples distributed from the center of the circle to the circumference, and an annular partition is arranged between the thermocouples.

9. The method for preparing a silicon-based microsphere array according to claim 8, characterized in that: The radius of the circular thermocouple is 50 mm; there are three annular thermocouples, and the ring widths of the annular thermocouples distributed from the center to the circumference are 25, 25, and 50 mm respectively.

10. The method for preparing a silicon-based microsphere array according to claim 9, characterized in that: The heating temperatures of the thermocouples distributed from the center to the circumference are set to 164°C, 165°C, 167°C, and 170°C respectively.

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