Quartz etching solution and etching method thereof

Abstract

The invention relates to the technical field of etching solutions, and particularly discloses a quartz etching solution and an etching method thereof.The quartz etching solution is prepared from, by mass, 18%-23% of hydrofluoric acid, 10%-12% of ammonium bifluoride, 1.5% of additives and the balance water; wherein the additive contains a surfactant and a cationic polymer. According to the etching solution provided by the invention, the additive contains the surfactant and the cationic polymer, and the surfactant has interface activation and foam inhibition effects in a strong acid environment and can reduce local interface tension and promote bubble stripping, so that local roughening caused by bubble shielding is reduced; the cationic polymer is weakly adsorbed on an etching interface to form a thin film, so that nucleation and growth of by-products (such as (NH4) 2SiF6) on the interface are inhibited, and particle deposition is reduced; the etching solution is used for etching quartz materials, the surface roughness of quartz is remarkably reduced while the high etching rate is guaranteed, and Ra is smaller than or equal to 120 nm during 200-micron deep etching.

Description

Technical Field

[0001] This invention relates to the field of etching solution technology, specifically to quartz etching solution and etching method, and is particularly suitable for the processing of quartz microstructures that require deep etching and controlled surface roughness. Background Technology

[0002] Quartz (SiO2, crystalline quartz or fused silica) is widely used in piezoelectric devices, microelectromechanical systems (MEMS), optical components, microfluidic chips, and sensors due to its excellent mechanical strength, thermal stability, electrical insulation, and good optical properties. With the increasing demand for micro / nano-structured devices and deep etching at the micrometer level, higher requirements are being placed on quartz etching processes: not only are high etching rates required to ensure processing efficiency, but also good surface finish (low roughness) and processing consistency must be maintained at greater etching depths.

[0003] Most existing etching solutions are optimized for silicon, glass, or shallow etching. While the types of additives involved (such as short-chain alcohols, IPA, conventional PEG, and some fluoroalkyl surfactants) can improve roughness under certain conditions, no cases have been published that simultaneously achieve high etching rate (≈0.7μm / min) and low roughness (≤120 nm) under deep etching (≥200μm) conditions. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a quartz etching solution and etching method that exhibits chemical stability in a strong acid and fluorine-containing environment while synergistically suppressing the deposition of bubbles and byproducts. Under deep etching conditions, it can maintain low roughness while also ensuring etching efficiency.

[0005] The technical solution of the present invention is a quartz etching solution comprising the following raw materials by mass percentage: 18-23% hydrofluoric acid, 10-12% ammonium hydrofluoride, 0.8-1.5% additives, and the remainder being water; wherein the additives contain surfactants and cationic polymers.

[0006] Optionally, the surfactant is lauramidopropyl hydroxysulfonate.

[0007] Optionally, the cationic polymer is polydimethyldiallylammonium chloride.

[0008] Optionally, the mass ratio of surfactant to cationic polymer in the additive is 19-29:1.

[0009] Optionally, the mass ratio of surfactant to cationic polymer in the additive is 19:1.

[0010] Optionally, the surfactant accounts for 0.76-1.45% of the etching solution.

[0011] Optionally, the cationic polymer accounts for 0.04-0.075% of the etching solution.

[0012] This invention also relates to a method for preparing the etching solution, the specific steps of which are as follows: Hydrofluoric acid, ammonium fluoride, and additives are added separately to water and mixed in an ice-water bath to obtain the final product.

[0013] The present invention also relates to a method for etching quartz materials using the above-mentioned etching solution. The quartz material to be etched is immersed in the quartz etching solution described in any one of claims 1-7, etched at 55-75°C, and then cleaned and dried to complete the operation.

[0014] The present invention also relates to etching times of 5 hours or more.

[0015] The present invention has the following beneficial effects: The etching solution provided by this invention contains surfactants and cationic polymers as additives. The surfactants have interfacial activation and antifoaming effects in a strong acid environment, which can reduce local interfacial tension and promote bubble removal, thereby reducing local roughness caused by bubble shielding. The cationic polymers form a thin film by weak adsorption at the etching interface, inhibiting the nucleation and growth of byproducts at the interface, such as byproduct (NH4)2SiF6, and reducing particle deposition. The two additives work synergistically, with the surfactants responsible for interfacial kinetic regulation and the cationic polymers responsible for inhibiting deposition / particle nucleation, thus simultaneously addressing the three factors that lead to increased roughness from a microscopic mechanism: bubbles, deposition, and local rate differences. When used for etching quartz materials, it ensures a high etching rate while significantly reducing the surface roughness of quartz, achieving Ra≤120 nm at a 200μm etching depth. Attached Figure Description

[0016] Figure 1 The effect of etching quartz using the etching solution in Comparative Example 6; Figure 2 This is the effect of etching quartz with the etching solution in Example 4. Detailed Implementation

[0017] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, all raw materials and reagents used are commercially available.

[0018] The quartz etching solution provided by this invention comprises the following raw materials by mass percentage: 18-23% hydrofluoric acid, 10-12% ammonium hydrofluoride, 0.8-1.5% additives, and the remainder being water; wherein the additives contain a surfactant and a cationic polymer. The surfactant is lauramidopropyl hydroxysulfonate betaine (LHS). The cationic polymer is polydiallyl ammonium chloride (PDADMAC).

[0019] In some embodiments, the mass ratio of surfactant to cationic polymer in the additive is 19 to 29:1. Preferably, it is 19:1.

[0020] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are only for illustrating the present invention and should not be regarded as limiting the scope of the present invention.

[0021] Preparation of quartz etching solution The composition and dosage of the additives in the following examples and comparative examples are shown in Table 1. Each raw material was weighed according to the specified proportions. At room temperature, ammonium bifluoride powder and the additives were added to deionized water. Hydrofluoric acid was then slowly added dropwise in an ice-water bath while stirring thoroughly to obtain the final product. The proportion of hydrofluoric acid in the etching solution was 23%, and the proportion of ammonium bifluoride in the etching solution was 12%.

[0022] The prepared etching solution was used to etch quartz sheets with dimensions of 1cm x 1cm. Roughness was measured using a 3D profilometer and a super depth-of-field microscope. The etching temperature was controlled at 60°C, the rotation speed at 300 r / min, and the etching time at 300 minutes. Specific etching details are shown in Table 1 below.

[0023] Table 1

[0024] Table 1 shows that the optimal etching effect is achieved when the mass ratio of additives LHS to PDADMAC is 19:1 and the addition amount is 1.5%. The best etching effect resulted in an etching depth of approximately 200 μm on the quartz wafer, with an Ra value of 99–120 nm. The etched surface was smooth, with no residual triangular pyramids. Comparative Examples 4 and 5 show that neither additive significantly reduced roughness when added individually. In Comparative Example 7, replacing LHS with an equal amount of betaine while keeping other conditions unchanged resulted in no significant reduction in roughness. In Comparative Example 8, replacing PDADMAC with an equal amount of ammonium chloride while keeping other conditions unchanged also resulted in no significant reduction in roughness.

[0025] When the total amount of additives added is higher than 1.5%, the solution is opaque and no etching test was conducted.

[0026] Figure 1In the comparison sample without additives, a large number of triangular pyramidal residues remained after etching, resulting in high roughness. Figure 2 After adding the optimal amounts of LHS and PDADMAC, the residual triangular pyramid disappeared, the roughness was reduced to 99.08nm, and the surface was smooth and uniform after etching.

[0027] The above embodiments describe preferred embodiments of the present invention, but the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other way. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A quartz etching solution, characterized in that: It includes the following raw materials by mass percentage: 18-23% hydrofluoric acid, 10-12% ammonium bifluoride, 0.8-1.5% additives, and the remainder being water; wherein the additives contain surfactants and cationic polymers.

2. The etching solution according to claim 1, characterized in that: The surfactant is lauramidopropyl hydroxysulfonate betaine.

3. The etching solution according to claim 1, characterized in that: The cationic polymer is polydimethyldiallylammonium chloride.

4. The etching solution according to claim 1, characterized in that: The mass ratio of surfactant to cationic polymer in the additive is 19~29:

1.

5. The etching solution according to claim 1, characterized in that: The mass ratio of surfactant to cationic polymer in the additive is 19:

1.

6. The etching solution according to claim 1, characterized in that: The surfactant accounts for 0.76-1.45% of the etching solution.

7. The etching solution according to claim 1, characterized in that: The cationic polymer accounts for 0.04-0.075% of the etching solution.

8. The method for preparing the etching solution according to any one of claims 1 to 7, characterized in that, The specific steps are as follows: Hydrofluoric acid, ammonium fluoride, and additives are added separately to water and mixed in an ice-water bath to obtain the final product.

9. A method for etching quartz materials using the etching solution according to any one of claims 1 to 7, characterized in that: The quartz material to be etched is immersed in the quartz etching solution described in any one of claims 1-7, etched at 55-75°C, and then cleaned and dried to complete the operation.

10. The etching method according to claim 9, characterized in that: The etching time is more than 5 hours.

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