A method for processing quartz three-dimensional structure

Abstract

The present invention relates to quartz materials, and more specifically, to a method for processing quartz three-dimensional structures. The method comprises employing any two or three of a quartz wet etching process, a quartz dry etching process, and a parallel etching process for side ridge repair. The method can address the processing incompatibility inherent in quartz three-dimensional structure processing, resulting in high precision, low cost, and high efficiency in quartz three-dimensional processing.

Description

Technical Field

[0001] The invention relates to quartz materials, and in particular to a method for processing quartz three-dimensional structures. Background Art

[0002] A wide variety of quartz etching processes exist, both domestically and internationally, with diverse approaches for processing three-dimensional structures such as quartz cantilever beams. Currently, the main methods used for processing quartz three-dimensional structures are mechanical machining, laser machining, dry etching, and wet etching. Mechanical and laser machining have limited processing quality and precision, making them unsuitable for processing quartz MEMS (Micro-Electro-Mechanical System) devices. Dry etching is costly and slow, and quartz dry etching equipment and processes are not yet mature. Wet etching offers small dimensions, high precision, high efficiency, and low cost. However, due to the anisotropic nature of quartz crystal etching, crystal ridges are generated on the sidewalls during the etching process, preventing the quartz structure from achieving perfect symmetry. This can lead to various errors in cantilever beam products, including quality asymmetry, structural asymmetry, and orthogonality errors. Traditional wet etching methods for smoothing side crystal ridges require modifying solution properties, adjusting the solution selectivity, and increasing the etching time. This process is time-consuming, complex, and requires difficult to maintain solution stability. Summary of the Invention

[0003] The present invention aims to solve at least one of the above technical problems.

[0004] The present invention provides a method for processing quartz three-dimensional structures, which can solve the corresponding processing inappropriateness introduced by the processing method. The method of the present invention makes the quartz three-dimensional processing outstandingly high in precision, low in cost, and high in efficiency.

[0005] A quartz three-dimensional structure processing method comprises adopting any two or three of a quartz wet etching process, a quartz dry etching process, and a parallel etching process for side ridge repair.

[0006] According to the quartz three-dimensional structure processing method provided by the present invention, the quartz wet etching process includes one or both of a through-etching process (complete release) and a pre-etching process (partial release of the area). The through-etching process completely releases and removes the unit structure on the quartz wafer, separating and releasing the individual three-dimensional structures. The pre-etching process pre-processes the functional areas or overall symmetrical structures of the three-dimensional structure.

[0007] According to an embodiment of the present invention, the through etching process uses a mixed solution of hydrofluoric acid and ammonium fluoride, preferably a mixed solution with a solution ratio of: 40wt% hydrofluoric acid solution: 40wt% ammonium fluoride solution = (1:4)-(3:1) (v / v), for example, 1:1 (v / v), and releases the area outside the mask area at a single stable temperature of 40-80°C (for example, 40°C, 50°C, 60°C, 70°C, 80°C) in a temperature environment to obtain a three-dimensional structure that meets the requirements.

[0008] According to an embodiment of the present invention, the pre-etching process uses a mixed solution of hydrofluoric acid and ammonium fluoride, preferably using a diluted solution of a mixed solution (v / v) with a solution ratio of: 40wt% hydrofluoric acid solution: 40wt% ammonium fluoride solution = (1:4)-(3:1), for example, 1:1 (v / v), and the dilution degree of the mixed solution is 1-10 times (v / v). At the same time, a single stable temperature environment of 10-60°C (for example, 10°C, 20°C, 30°C, 40°C, 50°C, 60°C) is maintained, and a gradient release is performed on the non-mask area to achieve a multi-level etching structure.

[0009] According to the quartz three-dimensional structure processing method provided by the present invention, the quartz dry etching process is used to adjust the sidewall angle generated by quartz wet etching and reduce the thickness of non-functional structures of the quartz wafer, while removing the mask layer on the surface of the three-dimensional pattern through the dry etching process.

[0010] According to an embodiment of the present invention, the process gas used in the quartz dry etching process is mainly one or two of C4F8 (octafluorocyclobutane) and CF4 gases, and the process rate of the process gas is preferably 5 μm / h-20 μm / h.

[0011] According to an embodiment of the present invention, the quartz dry etching process etches the mask metal layer.

[0012] According to the quartz three-dimensional structure processing method provided by the present invention, the parallel etching process for side ridge repair is a wet etching secondary processing to (greatly) reduce the height and width of the quartz side wall crystal ridges, so that the side wall crystal ridges are completely eliminated.

[0013] According to an embodiment of the present invention, the parallel etching method for repairing side ridges uses a mixed solution of hydrofluoric acid and ammonium fluoride, preferably with a solution ratio of: 40wt% hydrofluoric acid solution: 50wt% ammonium fluoride solution = (1-2):1 (v / v), for example, 1:1 (v / v); the process temperature is 40°C-70°C, for example, 40°C, 50°C, 60°C, 70°C. The etching time is preferably 20-40 hours, for example, 20 hours, 30 hours, or 40 hours.

[0014] According to the method for processing quartz three-dimensional structures provided by the present invention, the quartz material includes any cut shape.

[0015] According to the quartz three-dimensional processing method provided by the present invention, the mask layer for dry etching acting on the quartz surface can be Au, Ag, Cr, photoresist, or polycrystalline silicon.

[0016] According to the quartz three-dimensional structure processing method provided by the present invention, the thickness of the quartz wafer used is in the range of 30 μm to 500 μm.

[0017] According to an embodiment of the present invention, when the thickness of the quartz wafer ranges from 200 μm to 1000 μm, a quartz wet etching process, a quartz dry etching process, and a parallel etching process are sequentially adopted.

[0018] According to an embodiment of the present invention, when the thickness of the quartz wafer ranges from 100 μm to 200 μm, a quartz dry etching process, a quartz wet etching process, and a parallel etching process are sequentially adopted.

[0019] According to an embodiment of the present invention, when the thickness of the quartz wafer ranges from 30 μm to 100 μm, a parallel etching process and a dry etching process are sequentially adopted.

[0020] According to the quartz three-dimensional structure processing method provided by the present invention, the quartz processing structure includes a cantilever beam structure, a multi-support beam structure, and a MESA crystal structure.

[0021] According to an embodiment of the present invention, the method further includes the step (1) of cleaning the quartz substrate sample to be processed (serving as a base layer); the cleaning can generally be performed according to a standard cleaning process in the art.

[0022] According to an embodiment of the present invention, the method further comprises depositing a metal layer, photoresist, or polycrystalline silicon on both sides of the quartz substrate sample to be processed (serving as a base layer), wherein the metal layer may be selected from Au, Ag, and Cr. The thickness of the metal layer, photoresist, or polycrystalline silicon may be 100-300 nm.

[0023] According to an embodiment of the present invention, the method further includes performing double-sided photolithography on a quartz substrate sample (serving as a base layer) on which a metal layer or photoresist or polycrystalline silicon is deposited on both sides to prepare a cantilever beam structure or a unit outer frame (for example, the photolithographic pattern is a projection-overlapping pattern) or a flexible beam (for example, the photolithographic pattern is a projection-overlapping pattern). Conventional processes in the art can generally be used, for example, the process flow includes sequentially performing coating, soft baking, photolithography, development, and film hardening.

[0024] According to an embodiment of the present invention, after the above step (3), the process further includes a step (4) of dry etching the above metal layer or photoresist or polycrystalline silicon to release the eroded area. Specifically, the above quartz dry etching process can be used.

[0025] According to an embodiment of the present invention, after the above step (4), the process further includes a step (5) of wet etching the release area, which can be specifically performed using the above quartz wet etching process.

[0026] According to an embodiment of the present invention, after the above step (5), a step (6) of removing the photoresist is further included. For example, a photoresist stripping solution is used to remove the wafer, and the wafer is washed with alcohol, ultrasonicated with deionized water, dried, and dried.

[0027] According to an embodiment of the present invention, after the above step (6), the step (7) of performing a double-sided dry etching process on the quartz substrate sample (serving as a base layer, such as the above metal layer or photoresist or polycrystalline silicon) is also included. Specifically, the above-mentioned quartz dry etching process can be used.

[0028] According to an embodiment of the present invention, the above steps 1-7 are repeated until the product structure is completely released, which is recorded as step (8).

[0029] According to an embodiment of the present invention, after the above step (8), a step (9) of performing a parallel etching process on the quartz substrate sample (serving as the base layer) to repair the side ridges can be further included. Specifically, the above parallel etching process for repairing the side ridges can be used.

[0030] The present invention also provides a three-dimensional quartz structure, which is manufactured by the above method.

[0031] The present invention provides a method for processing quartz three-dimensional structures, including a quartz wet etching process, a dry etching process, and a parallel etching process for side ridge repair. The wet etching of the quartz material is anisotropic. Because the angle of the side crystal edges formed by the quartz wet etching in a specific solution is fixed, the initial thickness of the quartz etching in the hollowed-out area is reduced during the processing of the quartz three-dimensional structure. This can effectively reduce the side crystal edges ultimately produced by the quartz three-dimensional structure and the structural asymmetry introduced during unit disassembly. At the same time, the dry etching process is used to remove the excess mask layer, effectively reducing the risk of excessive side etching introduced by wet etching. This invention significantly improves the product quality of high-precision cantilever beam structures, multi-support beam structures, and MESA crystal structures, bringing a qualitative improvement to the development of quartz MEMS products towards high precision. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1: Schematic diagram of the quartz three-dimensional structure processing method according to embodiment 1 of the present invention. DETAILED DESCRIPTION

[0033] The following examples are intended to illustrate the present invention but are not intended to limit the scope of the invention. Where specific techniques or conditions are not specified in the examples, the methods were performed according to those described in the literature in the art or according to the product instructions. Where the manufacturer of the reagents or instruments is not specified, all are conventional products available through regular channels.

[0034] Example 1

[0035] This embodiment provides a method for processing a three-dimensional quartz structure, comprising the following steps:

[0036] 1. Take a Z-cut quartz substrate sample with a flat surface and a thickness of 300μm as the base layer. According to the standard cleaning process, it is washed with alcohol, alkali, and acid for 20 minutes each. Then, it is ultrasonically cleaned in deionized water for 10 minutes, rinsed with deionized water for 3 minutes, and then dried and dried.

[0037] 2. Use a sputtering coating machine to deposit a Cr layer on both sides of the quartz wafer to be coated with a thickness of 300nm, and then perform an annealing process on the wafer after the coating process. The annealing parameters are 180℃ for 1 hour.

[0038] 3. Use the standard photolithography process to perform double-sided photolithography to prepare the cantilever beam structure. The photolithography pattern is a projection overlap pattern. The process flow is to perform photoresist coating, soft baking, photolithography, development, and hardening.

[0039] 4. Use dry etching to etch the Cr layer, releasing the wet etching area. The process gas used is C4F8, and the process rate is 5μm / h.

[0040] 5. Use a mixed solution of 40 wt % hydrofluoric acid solution: 40 wt % ammonium fluoride solution = 1:1 (v / v) (heated to 70° C.) to wet etch the release area to a single-sided etching depth of 30 μm.

[0041] 6. Use photoresist stripping solution to remove photoresist from the wafer, and then wash the wafer with alcohol, ultrasonicate with deionized water, spin dry, and dry it.

[0042] 7. Perform a quartz dry etching process on both sides of the quartz, with a single-side etching depth of 20 μm. The process gas used is C4F8, and the process rate is 5 μm / h.

[0043] 8. Repeat steps 1-7 until the product structure is completely released.

[0044] 9. Using a mixed solution of 40 wt % hydrofluoric acid solution: 40 wt % ammonium fluoride solution = 1:1 (v / v) (heated to 50° C.), the cantilever beam structure was etched for 20 hours to obtain a cantilever beam with a structure close to the ideal structure, i.e., the sidewalls of the cantilever beam in the X and Y directions were free of crystal edges.

[0045] Example 2

[0046] This embodiment provides a method for processing a three-dimensional quartz structure, comprising the following steps:

[0047] 1. Take a 100μm thick AT-cut quartz substrate sample with a flat surface as the base layer. According to the standard cleaning process, perform alcohol washing, alkali washing, and acid washing for 20 minutes each. Then, ultrasonically clean it in deionized water for 10 minutes, rinse it with deionized water for 3 minutes, spin dry, and dry it.

[0048] 2. Use a sputtering coating machine to deposit a Cr layer on both sides of the quartz wafer to be coated with a thickness of 100nm, and then perform an annealing process on the wafer after the coating process. The annealing parameters are 180℃ for 1 hour.

[0049] 3. Use the standard photolithography process to perform double-sided photolithography to prepare the unit frame. The photolithography pattern is a projection overlap pattern. The process flow is to perform photoresist coating, soft baking, photolithography, development, and hardening.

[0050] 4. Dry-etch the Cr layer using C4F8 as the process gas at a rate of 5 μm / h. Release the wet-etched area. Then, wet-etch the thinned area using a mixed solution of 40 wt% hydrofluoric acid solution and 40 wt% ammonium fluoride solution (1:1 v / v) heated to 70°C. The single-sided etching depth was 48 μm.

[0051] 5. According to the standard cleaning process, the photoresist of the wet-etched wafer is removed, and then alcohol washing, alkaline washing, and acid washing are carried out in sequence for 20 minutes each, and then rinsed with deionized water for 3 minutes, dried, and dried.

[0052] 6. Use the standard photolithography process to perform double-sided photolithography to prepare the MESA structure. The photolithography pattern is a projection overlap pattern. The process flow is to perform photoresist coating, soft baking, photolithography, development, and hardening.

[0053] 7. Perform double-sided quartz dry etching (the process gas used is C4F8, the process rate is 5μm / h), and the single-sided etching depth is 0.5-1μm.

[0054] 8. After the structural processing is completed, a complete MESA structure is obtained. The appearance of the MESA structure is intact, the frequency of the high-frequency crystal is controllable, and the surface warping and roughness meet the CMP product effect.

[0055] Example 3

[0056] This embodiment provides a method for processing a three-dimensional quartz structure, comprising the following steps:

[0057] 1. Take a Z-cut quartz substrate sample with a flat surface and a thickness of 90μm as the base layer. According to the standard cleaning process, it is washed with alcohol, alkali, and acid for 20 minutes each, rinsed with deionized water for 3 minutes, and then dried and dried.

[0058] 2. Use a sputtering coating machine to deposit a Cr layer on both sides of the quartz wafer to be coated with a thickness of 300nm, and then perform an annealing process on the wafer after the coating process. The annealing parameters are 180℃ for 1 hour.

[0059] 3. Use the standard photolithography process flow to perform double-sided photolithography to prepare the wet release area of ​​the flexible beam with a width of 20μm. The photolithography pattern is a projection overlap pattern. The process flow is to perform photoresist coating, soft baking, photolithography, development, and hardening.

[0060] 4. Etch the Cr layer using a dry etching process, using C4F8 as the process gas and a process rate of 5 μm / h.

[0061] 5. According to the standard cleaning process, carry out alcohol washing, alkali washing and acid washing for 20 minutes each, then rinse in deionized water for 3 minutes, spin dry and dry.

[0062] 6. Use photoresist stripping solution to remove photoresist from the wafer, and then wash the wafer with alcohol, ultrasonicate with deionized water, spin dry, and dry it.

[0063] 7. Perform double-sided quartz dry etching, with a single-sided etching depth of 50 μm. The process gas used is C4F8, and the process rate is 5 μm / h.

[0064] 8. Then, a mixed solution of 40 wt% hydrofluoric acid solution: 40 wt% ammonium fluoride solution = 1:1 (v / v) (heated to 70°C) was used to wet etch the released area to complete the parallel etching process for side edge repair, and finally a flexible beam with a width of 50 μm and a thickness of 50 μm was obtained. The final surface roughness of the flexible beam was less than 30 nm.

[0065] Example 4

[0066] This embodiment provides a method for processing a three-dimensional quartz structure, comprising the following steps:

[0067] 1. Take a Z-cut quartz substrate sample with a flat surface and a thickness of 500μm as the base layer. According to the standard cleaning process, it is washed with alcohol, alkali, and acid for 20 minutes each. Then, it is ultrasonically cleaned in deionized water for 10 minutes, rinsed with deionized water for 3 minutes, and then dried and dried.

[0068] 2. Use a sputtering coater to deposit a 200nm thick Cr layer on both sides of the quartz wafer to be coated. Then, anneal the wafer after the coating process at 180°C for 1 hour.

[0069] 3. Use the standard photolithography process flow to perform double-sided photolithography to prepare the wet release area of ​​the flexible beam with a width of 20μm. The photolithography pattern is a projection overlap pattern. The process flow is to perform photoresist coating, soft baking, photolithography, development, and hardening.

[0070] 4. Use dry etching to etch the Cr layer, releasing the wet etching area. The process gas used is C4F8, and the process rate is 5μm / h.

[0071] Then, a mixed solution of 40 wt % hydrofluoric acid solution: 40 wt % ammonium fluoride solution = 1:1 (v / v) (heated to 70° C.) is used to wet etch the release area until the product is just etched through.

[0072] 5. The wafer that has been wet-etched is dry-etched using a dry etching process (the process gas used is C4F8, and the process rate is 5μm / h). The excess quartz in the etched area is etched cleanly to obtain a cantilever beam structure with vertical side walls. The side walls of the cantilever beam are smooth, the side wall crystal edge height is less than 5um, and the crystal edge width is less than 50um, which is infinitely close to a vertical cantilever beam structure.

[0073] Comparative Example 1

[0074] This comparative example provides a method for processing a three-dimensional quartz structure, comprising the following steps:

[0075] Step 1: Take a Z-cut quartz substrate sample with a flat surface and a thickness of 150μm as the base layer. According to the standard cleaning process, perform alcohol washing, alkali washing, and acid washing in sequence for 20 minutes each, then ultrasonically clean it in deionized water for 10 minutes, rinse it with deionized water for 3 minutes, spin dry, and dry it.

[0076] Step 2: Use a sputtering coating machine to deposit a Cr layer on both sides of the quartz wafer to be coated with a thickness of 300nm, and then perform an annealing process on the wafer after the coating process. The annealing parameters are 180℃ for 1 hour.

[0077] Step 3: Use the standard photolithography process to perform double-sided photolithography to prepare the cantilever beam structure. The photolithography pattern is a projection overlap pattern. The process flow is to perform photoresist coating, soft baking, photolithography, development, and hardening.

[0078] Step 4: Use a dry etching process to etch the Cr layer (the process gas used is C4F8, and the process rate is 5μm / h), use a photoresist stripping solution to remove the photoresist from the wafer, and then wash the wafer with alcohol, ultrasonicate with deionized water, spin dry, and dry it.

[0079] Step 5: Perform multiple dry etching processes on the quartz wafer (the process gas used is C4F8, and the process rate is 5μm / h.), with a single etching depth of 10μm and an etching time of one hour. After a single etching is completed, repeat steps 1 to 5 until the etching depth reaches 80μm.

[0080] Step 6: Turn the product over and repeat step 5.

[0081] Step 7: Finally, the etched cantilever beam is obtained. The side smoothness of the cantilever beam is poor, and the surface roughness of the mask area is greater than 50nm. The upper and lower surfaces are too rough, and the side wall parallelism is poor, so the ideal structure cannot be obtained.

[0082] Comparative Example 2

[0083] This comparative example provides a method for processing a three-dimensional quartz structure, comprising the following steps:

[0084] A Z-cut quartz substrate sample with a flat surface and a thickness of 150 μm was used as the base layer. According to the standard cleaning process, it was washed with alcohol, alkali, and acid for 20 minutes each, then ultrasonically cleaned in deionized water for 10 minutes, rinsed with deionized water for 3 minutes, and dried.

[0085] A sputtering coater was used to deposit a 100 nm thick Cr layer on both sides of the quartz wafer to be coated. The coated wafer was then annealed at 180°C for 1 hour.

[0086] The cantilever beam structure is prepared by double-sided photolithography using the standard photolithography process. The photolithography pattern is a projection overlap pattern. The process flow is to perform photoresist coating, soft baking, photolithography, development, and hardening.

[0087] The Cr layer is etched using a dry etching process, and the photoresist on the wafer is removed using a photoresist stripping solution. The wafer is then washed with alcohol, ultrasonically treated with deionized water, spun dry, and dried.

[0088] A mixed solution (heated to 70° C.) of 40 wt % hydrofluoric acid solution: 40 wt % ammonium fluoride solution = 1:1 (v / v) was used to wet etch the release area until the area was completely etched.

[0089] Finally, the etched cantilever beam is obtained. Due to the fixed angle of the crystal structure, the side ridge thickness of the obtained cantilever beam is relatively large, which is 1 / 5 of the substrate thickness (30μm), while the side ridge thickness obtained in Example 1 is 1 / 10 (10-15μm). The ridge thickness is much greater than that in Example 1, and the process time is 1.4 times that of Example 1.

[0090] Although the present invention has been described in detail above using general descriptions and specific embodiments, it will be apparent to those skilled in the art that modifications and improvements may be made based on the present invention. Therefore, such modifications and improvements, which do not depart from the spirit of the present invention, are intended to be within the scope of protection claimed herein.

Claims

1. A method for processing a quartz three-dimensional structure, characterized in that: When the thickness of the quartz wafer ranges from 200μm to 1000μm, the quartz wet etching process, the quartz dry etching process, and the parallel etching process for side edge repair are used in sequence; The quartz wet etching process is a through etching process, using a mixed solution of hydrofluoric acid and ammonium fluoride, with a solution ratio of 40wt% hydrofluoric acid solution: 40wt% ammonium fluoride solution = 1:1 v / v. Under a single stable temperature of 70°C, the area outside the mask area of ​​the quartz wafer is released to obtain a three-dimensional structure that meets the requirements; The quartz dry etching process is used to adjust the sidewall angle produced by the quartz wet etching and reduce the thickness of the non-functional structure of the quartz wafer, while removing the mask layer on the surface of the three-dimensional structure through the dry etching process; The parallel etching process for side edge repair is a secondary wet etching process to reduce the height and width of the quartz side wall crystal edges so that the side wall crystal edges are completely eliminated; The parallel etching process for side edge repair uses a mixed solution of hydrofluoric acid and ammonium fluoride, with a solution ratio of: 40wt% hydrofluoric acid solution: 50wt% ammonium fluoride solution = 1:1 v / v; the process temperature is 50°C; and the etching time is 20-40 hours.

2. The method for processing a three-dimensional quartz structure according to claim 1, wherein: The process gas used in the quartz dry etching process is one or both of C4F8 and CF4 gases.

3. The method for processing a three-dimensional quartz structure according to claim 2, wherein: The process rate of the process gas is 5 μm / h-20 μm / h.

4. The method for processing a quartz three-dimensional structure according to any one of claims 1 to 3, characterized in that: The mask layer for dry etching on the quartz surface is Au, Ag, Cr, photoresist or polysilicon; and / or, The quartz three-dimensional structure includes a cantilever beam structure, a multi-support beam structure or a MESA crystal structure.

5. A quartz three-dimensional structure, characterized in that: Made by the method according to any one of claims 1 to 4.

Images