Preparation method of glass containing holes with high depth-diameter ratio

Abstract

The invention discloses a preparation method of glass containing holes with high aspect ratio. The preparation method comprises the following steps: (1) pretreating a glass substrate; (2) irradiating the target area of the glass substrate by using ultrafast laser to form a denaturation area; (3) coating photoresist on the upper surface and the lower surface of the glass substrate; (4) performing exposure treatment after the step (3); (5) after the step (4), carrying out developing treatment to expose the denatured region; and (6) carrying out dry etching on the denatured area on the glass substrate to obtain the glass containing the holes with high depth-diameter ratio, and reacting gases for dry etching are fluorine-based gases and oxygen. According to the preparation method disclosed by the invention, the high-precision processing of ultrafast laser, the fine mask protection effect of photoresist and the fine control of dry etching are ingeniously combined, so that the glass containing the holes with the high aspect ratio can be efficiently prepared with high precision.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor packaging, and in particular relates to a method for preparing glass containing holes with a high aspect ratio. Background Art

[0002] The interposer is a core component in three-dimensional integrated microsystems. Its main function is to provide high-density interconnection between chips and integrate passive components. The interposer is usually made of silicon, glass or other high-dielectric constant materials, and the signal interconnection between the upper and lower surfaces of the substrate is achieved by processing vertical through holes on it. The interposer plays a vital role in three-dimensional integration technology, and its importance can be compared with the silicon substrate in Moore's era.

[0003] Laser induced etching technology is a common method for processing glass through holes. It combines ultrafast laser with wet etching to quickly process through holes on glass substrates. This technology has unique advantages in preparing high aspect ratio structures and internal channels. Although ultrafast laser processing has high processing accuracy, due to the isotropic properties of glass, lateral corrosion during wet etching is difficult to avoid, which affects the processing accuracy. At the same time, factors such as the concentration and temperature of the etchant and the composition of the glass during wet etching will affect the etching rate and quality, making it difficult to accurately control the processing process, especially in the case of high aspect ratios, such as when the aspect ratio reaches 15:1 to 20:1, it becomes increasingly difficult to control the etching conditions to obtain through holes that meet the requirements.

[0004] Therefore, there is an urgent need for a method for preparing glass containing holes with a high aspect ratio to solve the deficiencies of the prior art. Summary of the invention

[0005] In view of the above problems, the purpose of the present invention is to provide a method for preparing glass containing high aspect ratio holes, which cleverly combines the high-precision processing of ultrafast lasers, the fine mask protection effect of photoresist and the fine control of dry etching, so that glass containing high aspect ratio holes can be prepared efficiently and with high precision.

[0006] To achieve the above objectives, the present invention provides a method for preparing glass containing holes with a high aspect ratio, the steps comprising:

[0007] (1) pre-treating the glass substrate;

[0008] (2) using an ultrafast laser to irradiate a target area of ​​a glass substrate to form a denatured area;

[0009] (3) coating photoresist on the upper and lower surfaces of the glass substrate;

[0010] (4) performing an exposure process after step (3);

[0011] (5) performing a development process after step (4) to reveal the denatured area;

[0012] (6) Dry etching the denatured area on the glass substrate to obtain glass containing holes with a high aspect ratio, wherein the reaction gases for the dry etching are fluorine-based gas and oxygen.

[0013] Compared with the prior art, the present invention firstly forms a denatured zone in the target area of ​​the glass substrate by ultrafast laser. This process utilizes the characteristics of short ultrafast laser pulse and high energy concentration, and can realize non-thermal melting modification on a micro scale, ensuring the accuracy of the shape of the denatured zone and the clarity of the edge. Subsequently, by uniformly coating the upper and lower surfaces of the glass substrate with photoresist and undergoing exposure and development processes, the denatured zone to be etched can be clearly and accurately exposed. Finally, in the dry etching stage, fluorine-based gas and oxygen are used as reaction gases, and the exposed denatured zone can be selectively etched. Since dry etching has the advantages of strong directionality and controllable etching rate, the depth and diameter ratio of the hole can be accurately controlled. At the same time, the photoresist also plays a key masking role in this process, effectively protecting the non-target area from the influence of the dry etching process, so that glass containing holes with high aspect ratio can be prepared efficiently and accurately. Therefore, the preparation method of the present invention skillfully combines the high-precision processing capability of ultrafast laser, the fine mask protection effect of photoresist and the fine control of dry etching technology, so that glass containing high aspect ratio holes can be prepared efficiently and with high precision.

[0014] Furthermore, the pretreatment of the present invention includes: ultrasonically cleaning and drying the glass substrate in a cleaning solution.

[0015] Furthermore, the energy of the ultrafast laser of the present invention is less than or equal to 200 μJ. When the energy of the ultrafast laser is limited to 200 μJ or less, the low-energy ultrafast laser can form a denatured zone on the glass substrate with extremely high spatial resolution and almost no heat diffusion effect.

[0016] Furthermore, step (3) of the present invention further comprises: coating photoresist on the upper and lower surfaces of the glass substrate, and then baking at 80-100° C. for 80-120 seconds.

[0017] Furthermore, step (4) of the present invention further comprises: performing an exposure treatment after step (3), and then baking at 110-122° C. for 70-100 seconds.

[0018] Furthermore, the exposure dose in step (4) of the present invention is 180 to 220 mJ / cm 2 .

[0019] Furthermore, the development treatment time in step (5) of the present invention is 40 to 50 seconds. Specifically, the development treatment can be performed using ZX-238 developer.

[0020] Furthermore, in step (6) of the present invention, the flow rate of the fluorine-based gas is 325-335 mL / min, the flow rate of the oxygen is 25-35 mL / min, and the etching rate of the dry etching is 288-300 nm / min.

[0021] Furthermore, in step (6) of the present invention, after dry etching, the step further includes performing a degumming treatment using a degumming liquid. Specifically, the degumming liquid may be N-methylpyrrolidone (NMP).

[0022] Furthermore, the root mean square roughness of the inner wall of the high aspect ratio hole of the present invention is less than or equal to 0.56 nm.

[0023] Furthermore, the aspect ratio of the high aspect ratio hole of the present invention is greater than 15:1. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The present invention is a process flow chart of a method for preparing glass containing holes with a high aspect ratio. DETAILED DESCRIPTION

[0025] In order to better illustrate the purpose, technical solution and beneficial effects of the present invention, the present invention will be further described below in conjunction with specific embodiments and drawings. It should be noted that the following implementation method is a further explanation of the present invention and should not be used as a limitation of the present invention.

[0026] Please refer to Figure 1 The present invention provides a method for preparing glass containing holes with a high aspect ratio, the steps comprising:

[0027] S1, pre-treating the glass substrate 11;

[0028] S2, using an ultrafast laser to irradiate a target area of ​​the glass substrate 11 to form a denatured area 12;

[0029] S3, coating the photoresist 13 on the upper and lower surfaces of the glass substrate 11;

[0030] S4, performing exposure treatment after step (3);

[0031] S5, performing a development process after step (4) to expose the denatured area 12;

[0032] S6, performing dry etching on the denatured area 12 on the glass substrate 11, wherein the reaction gas for the dry etching is fluorine-based gas and oxygen;

[0033] S7, using a degumming liquid to perform degumming treatment;

[0034] S8. Obtain glass containing holes 14 with a high aspect ratio.

[0035] Wherein, the pretreatment in step S1 includes: ultrasonically cleaning and drying the glass substrate in a cleaning solution. Specifically, the cleaning solution includes but is not limited to water and alkali solution. Specifically, ultrasonic cleaning is performed with 1-5wt% alkali solution for 5-15 minutes, and then ultrasonic cleaning is performed in water for 5-10 minutes, and the ultrasonic frequency is 10-50kHz. Specifically, the drying temperature is 115-125°C, and the drying time is 10-20 minutes. Specifically, the drying temperature may be but is not limited to 115°C, 116°C, 117°C, 120°C, 122°C, 124°C, 125°C; the drying time may be but is not limited to 10 minutes, 12 minutes, 15 minutes, 18 minutes, 20 minutes.

[0036] The ultrafast laser in step S2 refers to a laser with a pulse width in the order of picoseconds (ps) or femtoseconds (fs), and specifically, the energy of the ultrafast laser is less than or equal to 200 μJ. When the energy of the ultrafast laser is limited to 200 μJ or less, the low-energy ultrafast laser can form a denaturation zone on the glass substrate with extremely high spatial resolution, and almost no heat diffusion effect will be generated, that is, the material outside the laser action area is almost not thermally damaged, and the original properties of the material are maintained, which is crucial to maintaining the integrity and functionality of the structure around the hole.

[0037] Wherein, step S3 also includes: coating the upper and lower surfaces of the glass substrate with photoresist, and then baking at 80-100°C for 80-120s. For example, it can be baked at 90°C for 90s, or it can be baked at 100°C for 90s. The pre-baking treatment can evaporate part of the solvent in the photoresist, making the photoresist more viscous, which helps to reduce the flow of the photoresist during subsequent processing, especially when exposing, to ensure that the thickness and shape of the photoresist layer are more uniform and stable. Specifically, the photoresist can be AZ5214 positive photoresist. Specifically, the photoresist can be applied to the upper and lower surfaces of the glass substrate by spin coating.

[0038] Wherein, step S4 also includes: performing exposure treatment after step (3), and then baking at 110-122° C. for 70-100 seconds. For example, it can be baked at 110° C. for 90 seconds, or it can be baked at 118° C. for 85 seconds. The post-baking treatment can induce a chemical reaction in the photoresist, thereby improving the mechanical strength of the photoresist. The photoresist with higher mechanical strength can better resist physical stress in the subsequent development and etching steps, reduce damage and deformation, which can ensure that holes with high aspect ratios can be prepared efficiently and accurately.

[0039] The exposure dose in step S4 is 180-220 mJ / cm 2 The exposure dose may be, but is not limited to, 180 mJ / cm 2 、190mJ / cm 2 、200mJ / cm 2 、210mJ / cm 2 、220mJ / cm 2 The precise control of exposure dose is the key factor to ensure the quality of photoresist patterning. The exposure dose is less than 180mJ / cm 2 When the exposure dose is higher than 220mJ / cm 2 The exposure dose is controlled at 180-220 mJ / cm 2 Within this range, the photoresist can form clear, high-contrast patterns, which is beneficial for subsequent development and etching steps and ensures the precise preparation of high aspect ratio holes.

[0040] The development time in step S5 is 40 to 50 seconds. For example, the development time may be, but is not limited to, 40 seconds, 45 seconds, 48 ​​seconds, or 50 seconds. Specifically, ZX-238 developer may be used for the development process.

[0041] Among them, the flow rate of fluorine-based gas in step S6 is 325-335 mL / min, the flow rate of oxygen is 25-35 mL / min, and the etching rate of dry etching is 288-300 nm / min. Fluorine-based gas refers to a gas containing fluorine, such as CF4 (carbon tetrafluoride), SF6 (sulfur hexafluoride), etc. This type of gas has a strong reactivity with silicon and oxygen and can effectively remove glass materials. Specifically, the flow rate of fluorine-based gas is within the range of 325-335 mL / min, which not only has enough fluorine-based gas supply to maintain a high etching rate, but also can avoid the high etching rate, which is difficult to control and easily causes the unevenness of the holes and the increase of the surface roughness. Therefore, the flow rate of fluorine-based gas is 325-335 mL / min to ensure the controllability and stability of the etching process. Specifically, oxygen plays an auxiliary role in the dry etching process. It can react with fluorine-based gas to generate volatile by-products, help remove polymers and residues generated during dry etching, and keep the surface of the holes clean and flat.

[0042] Wherein, after the dry etching in step S6, a degumming treatment is further performed using a degumming liquid, and specifically, the degumming liquid may be N-methylpyrrolidone (NMP).

[0043] The RMS roughness of the inner wall of the high aspect ratio hole in step S8 is less than or equal to 0.56 nm. Low inner wall roughness means that during the dry etching process, the etching rate is consistent at different parts of the hole, that is, the shape of the obtained hole is consistent.

[0044] Wherein, the aspect ratio of the high aspect ratio hole in step S8 is greater than 15:1.

[0045] The technical solution of the present application is described in detail below in conjunction with specific embodiments.

[0046] Example 1

[0047] This embodiment provides a method for preparing glass containing holes with a high aspect ratio, the steps comprising:

[0048] (1) The glass substrate was cleaned in a 5 wt % alkali solution by ultrasonic cleaning (20 kHz) for 10 min, then ultrasonic cleaning (30 kHz) in water for 7 min, and then dried at 120° C. for 15 min;

[0049] (2) using an ultrafast femtosecond laser to irradiate the target area of ​​the glass substrate to form a circular denatured area, wherein the laser parameters are: energy of 150 μJ, pulse width of 200 fs, frequency of 350 kHz, and single pulse;

[0050] (3) coating the upper and lower surfaces of the glass substrate with AZ5214 positive photoresist by spin coating, and then baking at 90° C. for 90 seconds;

[0051] (4) The exposure was performed using an MLA100 maskless lithography machine with an exposure dose of 200 mJ / cm 2 ;

[0052] (5) developing with ZX-238 developer to reveal the denatured area;

[0053] (6) performing dry etching on the denatured area on the glass substrate, wherein the parameters of the dry etching are: flow rates of fluorine-based gas and oxygen are 330 mL / min and 30 mL / min, respectively, the chamber pressure is 4 Pa, the radio frequency power is 300 W, and the etching rate is 292.3 nm / min;

[0054] (7) Using N-methylpyrrolidone for degumming treatment, a glass containing holes with a high aspect ratio is obtained.

[0055] Comparative Example 1

[0056] This comparative example provides a method for preparing glass containing holes with a high aspect ratio, the steps comprising:

[0057] (1) The glass substrate was cleaned in a 5 wt % alkali solution by ultrasonic cleaning (20 kHz) for 10 min, then ultrasonic cleaning (30 kHz) in water for 7 min, and then dried at 120° C. for 15 min;

[0058] (2) using an ultrafast femtosecond laser to irradiate the target area of ​​the glass substrate to form a circular denatured area, wherein the laser parameters are: energy of 150 μJ, pulse width of 200 fs, frequency of 350 kHz, and single pulse;

[0059] (3) coating the upper and lower surfaces of the glass substrate with AZ5214 positive photoresist by spin coating, and then baking at 90° C. for 90 seconds;

[0060] (4) The exposure was performed using an MLA100 maskless lithography machine with an exposure dose of 200 mJ / cm 2 ;

[0061] (5) developing with ZX-238 developer to reveal the denatured area;

[0062] (6) using an argon ion beam to perform high-energy ion beam etching on the denatured area on the glass substrate, wherein the radio frequency power is 300 W and the etching rate is 2 μm / min;

[0063] (7) Using N-methylpyrrolidone for degumming treatment, a glass containing holes with a high aspect ratio is obtained.

[0064] The glass containing holes with high aspect ratio in Example 1 and Comparative Example 1 was fixed on the sample stage of a Keyence VK-3000 microscope, and the contour of the through hole was clearly visible by adjusting the focal length and viewing angle of the microscope, and the hole depth, the diameter of the top and bottom of the hole were measured respectively by using the coordinate reading system of the microscope, and the root mean square roughness value of the surface was obtained by software analysis, and the measurement results are shown in Table 1. Specifically, the diameter ratio of the top to the bottom of the hole is closer to 1, that is, the hole is closer to a columnar shape, indicating better verticality.

[0065] Table 1 Measurement results of holes in Example 1 and Comparative Example 1

[0066]

[0067] As can be seen from Table 1, the preparation method of the present invention cleverly combines the high-precision processing capability of ultrafast lasers, the fine mask protection effect of photoresists, and the fine control of dry etching technology, thereby being able to efficiently and accurately prepare glass containing holes with a high aspect ratio.

[0068] Comparing Example 1 with Comparative Example 1, it can be seen that if dry etching is adjusted to high-energy ion beam etching, it can be seen that the roughness of the inner wall of the hole after high-energy ion beam etching is much higher than that of dry etching. This is because more polymers and residues will be produced during high-energy ion beam etching, and these substances will adhere to the surface of the hole, increasing the surface roughness. At the same time, the incident angle and energy distribution of the high-energy ion beam are prone to unevenness, resulting in inconsistent etching rates at the bottom and side walls of the hole, thereby affecting the depth-to-diameter ratio of the hole, making it difficult to achieve a depth-to-diameter ratio of more than 15:1. In addition, it is also easy to cause the inclination of the side walls of the hole to affect the verticality of the hole, and the physical bombardment of the ion beam may also cause microscopic defects on the surface of the hole, further affecting the verticality of the hole.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for preparing glass containing holes with a high aspect ratio, characterized in that the steps include: (1) pre-treating the glass substrate; (2) using an ultrafast laser to irradiate a target area of ​​the glass substrate to form a denatured area; (3) coating photoresist on the upper and lower surfaces of the glass substrate; (4) performing an exposure process after step (3); (5) performing a development process after step (4) to expose the denatured area; (6) Dry etching the modified area on the glass substrate to obtain glass containing holes with a high aspect ratio, wherein the reaction gas for dry etching is fluorine-based gas and oxygen.

2. The method for preparing glass containing holes with high aspect ratio according to claim 1, characterized in that: The energy of the ultrafast laser is less than or equal to 200 μj.

3. The method for preparing glass containing holes with high aspect ratio according to claim 1, characterized in that: Step (3) also includes: coating photoresist on the upper and lower surfaces of the glass substrate, and then baking at 80-100° C. for 80-120 seconds.

4. The method for preparing glass containing holes with high aspect ratio according to claim 1, characterized in that: Step (4) also includes: performing exposure treatment after step (3), and then baking at 110-122° C. for 70-100 seconds.

5. The method for preparing glass containing holes with high aspect ratio according to claim 1, characterized in that: The exposure dose in step (4) is 180-220 mJ / cm 2 .

6. The method for preparing glass containing holes with high aspect ratio according to claim 1, characterized in that: The development treatment time in step (5) is 40 to 50 seconds.

7. The method for preparing glass containing holes with high aspect ratio according to claim 1, characterized in that: In step (6), the flow rate of the fluorine-based gas is 325-335 mL / min, the flow rate of the oxygen is 25-35 mL / min, and the etching rate of the dry etching is 288-300 nm / min.

8. The method for preparing glass containing holes with high aspect ratio according to claim 1, characterized in that: The dry etching in step (6) also includes a degumming process using a degumming solution.

9. The method for preparing glass containing holes with high aspect ratio according to claim 1, characterized in that: The root mean square roughness of the inner wall of the high aspect ratio hole is less than or equal to 0.56 nm.

10. The method for preparing glass containing holes with high aspect ratio according to claim 1, characterized in that: The high aspect ratio hole has an aspect ratio greater than 15:1.

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