Gradient-structure nanofiber membrane material with high-precision purification effect and preparation method of gradient-structure nanofiber membrane material

Abstract

The invention discloses a gradient structure nanofiber membrane material with a high-precision purification effect and a preparation method, and the method comprises the following steps: preparing a PVDF nanofiber membrane by adopting an electrostatic spinning method, and controlling the prepared PVDF nanofiber membrane to have a double-layer composite gradient structure by regulating spinning parameters in the spinning process, the double-layer composite gradient structure comprises a surface layer and an inner layer, the surface layer is used for making contact with liquid to be purified firstly, the inner layer is connected with the surface layer and used for outputting purified liquid, the diameter of nanofibers and the pore diameter of a fiber membrane in the surface layer are large, and the diameter of nanofibers and the pore diameter of the fiber membrane in the inner layer are small; therefore, double gradients of fiber diameter and fiber membrane aperture are formed in the PVDF nanofiber membrane. The fiber membrane has a high-precision purification and removal effect on particulate matters in liquid, and can be particularly applied to the fields of semiconductor manufacture procedures and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of nanofiber nonwovens and liquid purification, and relates to a selective filtration nanofiber membrane material and a preparation method thereof, and in particular to a gradient structure nanofiber membrane material with high-precision purification effect and a preparation method thereof. Background Art

[0002] Semiconductor manufacturing is a series of important processes for producing chips, including cleaning, deposition, photolithography, etching, diffusion and other processes. During the semiconductor manufacturing and polishing process, abrasives, polishing fluids, environmental or human factors, chemical reagent residues, and metal parts of assembly equipment (such as polishing machines, cleaning machines, etc.) will produce various metal particles due to wear or corrosion, including: iron (Fe), copper (Cu), aluminum (Al), chromium (Cr), tungsten (W), titanium (Ti), sodium (Na), potassium (K), lithium (Li), aluminum oxide (Al2O3), cerium oxide (CeO2) and other metal oxide particles. The size of these metal particles is 0.02-1.0μm, and the particle concentration is as high as 10 15 / mL, metal particles will be embedded in the wafer surface during the polishing process, causing the wafer surface roughness to increase and forming micro scratches; metal particles embedded in the wafer surface can cause circuit short circuits and semiconductor device failure.

[0003] In addition, the oxides or hydroxides of metal elements such as Fe, Cu, and Al contained in semiconductor processes and polishing fluids will dissolve in acidic or alkaline environments, releasing corresponding metal ions. The surface of the polished semiconductor material (such as silicon wafer) will dissolve trace amounts of metal ions, such as K, due to the chemical action of the polishing fluid. + (≥110ppb), Na + (≥70ppb), Zn 2+ (≥20ppb), Ca 2+ (≥12ppb), Fe 2+ (≥4ppb), Fe 3+ (≥4ppb), Al3+ (≥3ppb), Cu 2+ (≥3ppb), etc.

[0004] When there is metal ion contamination on the wafer, it will not only cause great harm to semiconductor components, but the metal ions will also affect the physical and chemical properties of the polishing liquid such as pH value, conductivity, redox properties, thereby affecting the polishing rate, surface roughness, polishing uniformity, increasing PN junction leakage current, reducing product yield and reliability, causing pollution, and reducing the performance and quality of semiconductor devices.

[0005] Based on this, the present invention addresses the technical bottleneck of low filtration efficiency of metal particles of different sizes in the semiconductor process, and designs and develops a high-precision filtration nanofiber membrane material, which can significantly improve the filtration efficiency of metal particles of different sizes in the semiconductor process, achieve high-precision filtration effect, and provide a new strategy for the effective removal of different metal particles in liquid environments. Summary of the Invention

[0006] The purpose of the present invention is to address the deficiencies of the existing technology and provide a gradient structure nanofiber membrane material with high-precision purification effect and a preparation method thereof. The material achieves excellent filtration performance through a double-layer composite gradient structure design and can be effectively applied in fields such as semiconductor processes.

[0007] The technical solution adopted in the present invention is as follows:

[0008] A method for preparing a gradient-structured nanofiber membrane material with a high-precision purification effect, wherein a PVDF nanofiber membrane is prepared by an electrospinning method, and the PVDF nanofiber membrane obtained by regulating the spinning parameters during the spinning process has a double-layer composite gradient structure, wherein the double-layer composite gradient structure includes a surface layer for first contacting the liquid to be purified and an inner layer connected to the surface layer for outputting the purified liquid, wherein the nanofiber diameter and the fiber membrane pore size in the surface layer are both larger, and the nanofiber diameter and the fiber membrane pore size in the inner layer are both smaller, thereby forming a double gradient of fiber diameter and fiber membrane pore size in the PVDF nanofiber membrane.

[0009] In the above technical solution, further, the electrospinning solution is a mixed solvent of tetrahydrofuran (THF) and dimethylformamide (DMF), the mass ratio of THF to DMF is 1:1, and the mass concentration of PVDF in the spinning solution is 8-15%.

[0010] Furthermore, the spinning parameters include spinning solution concentration, spinning voltage, syringe speed, receiving roller speed, receiving distance and fiber web stacking time. By regulating these spinning parameters of the surface layer and inner layer, the fiber diameter, pore size and thickness of the surface layer and inner layer nanofiber membrane are controlled to present a precise gradient distribution structure.

[0011] Furthermore, when preparing the surface layer, the spinning parameters are controlled as follows: the spinning solution concentration is 12-15%, the spinning voltage is 15-20kV; the injector speed is 1.0-3.0mL / min; the receiving roller speed is 100-200 rpm; the receiving distance is 10-20cm, and the fiber web stacking time is 2-3h; when preparing the inner layer, the spinning parameters are controlled as follows: the spinning solution concentration is 8-11%, the spinning voltage is 20-30kV; the injector speed is 4.0-5.0mL / min; the receiving roller speed is 200-300 rpm; the receiving distance is 20-30cm, and the fiber web stacking time is 3-4h.

[0012] Furthermore, the average diameter of the PVDF nanofiber membrane is 0.45 to 0.5 μm, and the overall thickness is 38 to 42 μm.

[0013] Furthermore, the fiber diameter of the surface layer of the PVDF nanofiber membrane is greater than 0.48 μm, and the fiber membrane diameter of the inner layer is less than 0.48 μm; the membrane pore size of the surface layer is greater than 2 μm, and the membrane pore size of the inner layer is less than 2 μm; the thickness of the surface layer is 19-21 μm, and the thickness of the inner layer is 19-21 μm.

[0014] The gradient structure nanofiber membrane material prepared by the present invention has a high-precision purification effect and can be used as a liquid filtration membrane in semiconductor manufacturing processes.

[0015] The beneficial effects of the present invention are:

[0016] The present invention successfully produces a PVDF nanofiber membrane with a double-layer composite gradient structure of surface and inner layers by using a constant pressure liquid supply electrospinning device and regulating the PVDF electrospinning process parameters. In the membrane material, the diameters of the PVDF nanofibers in the surface and inner layers and the pore sizes of the fiber membrane are different, forming a gradient. The fiber diameter in the surface layer is large and the pore size of the fiber membrane is large, while the fiber diameter in the inner layer is small and the pore size of the fiber membrane is small. In particular, the optimal effect is achieved when the surface fiber diameter is greater than 0.48μm, the membrane pore size is greater than 2μm, and the thickness is about 20μm, while the inner layer nanofiber diameter is less than 0.48μm, the membrane pore size is less than 2μm, and the thickness is about 20μm. The composite gradient structure fiber membrane material with a double-layer composite gradient structure directly produced by this method has a gradient change in fiber diameter and pore size. The fiber diameter and pore size of the surface layer PVDF nanofiber membrane are larger, mainly to improve the rapid passage efficiency of liquid and increase liquid flux, while the fiber diameter and pore size of the inner layer PVDF nanofiber membrane are smaller, and the core is used to improve the interception effect and filtration efficiency of particulate matter in the liquid. The double-layer composite gradient structure PVDF nanofiber membrane prepared by the present invention has excellent filtration performance, and the filtration efficiency for SiO2 particles can be as high as 99.77%. It can be particularly used in application scenarios with high requirements for filtration, such as semiconductor processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is the structural diagram of the surface fibers of the PVDF nanofiber membrane.

[0018] Figure 2 This is the structural diagram of the inner layer fibers of the PVDF nanofiber membrane.

[0019] Figure 3 This is a comparison chart of the actual filtration effect of the PVDF nanofiber membrane of the present invention and the model simulation results.

[0020] Figure 4 These are SEM images of the upper and lower surfaces of the PVDF nanofiber membrane after filtration.

[0021] Figure 5 is the filtration efficiency of PVDF nanofiber membrane for filtrates of different concentrations under different pressure differences.

[0022] Figure 6 These are a series of PVDF nanofiber membrane samples prepared using the method of the present invention. DETAILED DESCRIPTION

[0023] The technical solution of the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0024] In an embodiment of the present invention, the electrospinning solution used is formulated as follows: the spinning solution is a mixed solvent of tetrahydrofuran (THF) and dimethylformamide (DMF), with THF / DMF = 1 / 1 (wt / wt), and the PVDF mass concentration in the spinning solution is 8-15%. The concepts of the present invention are applicable to other types of spinning solutions.

[0025] Example 1

[0026] PVDF nanofiber membranes were prepared using an electrospinning device. The spinning solution concentration was 8%, the spinning voltage was 15 kV, the syringe speed was 1.0 mL / min, the receiving roller speed was 100 rpm, the receiving distance was 10 cm, and the web layup time was 30 minutes. The resulting nanofiber membrane had a thickness of approximately 20 μm, and the filtration efficiency was only 80%.

[0027] Example 2

[0028] PVDF nanofiber membranes were prepared using an electrospinning device. The spinning solution concentration was 12%, the spinning voltage was 18 kV, the syringe speed was 2.0 mL / min, the receiving roller speed was 300 rpm, the receiving distance was 30 cm, and the web layup time was 60 minutes. The resulting nanofiber membrane had a thickness of approximately 20 μm and a filtration efficiency of only 84%.

[0029] Example 3

[0030] PVDF nanofiber membranes were prepared using an electrospinning device. The spinning dope concentration was 15%, the spinning voltage was 15 kV, the syringe speed was 1.0 mL / min, the receiving roller speed was 100 rpm, and the receiving distance was 20 cm. The web layup time was increased to 1.5 hours, resulting in a surface layer with a thickness of 40 μm and a filtration efficiency of 86%.

[0031] Example 4

[0032] PVDF nanofiber membranes were prepared using an electrospinning device. The spinning solution concentration was 8%, the spinning voltage was 18 kV, the syringe speed was 5.0 mL / min, the receiving roller speed was 300 rpm, and the receiving distance was 20 cm. The web layup time was increased to 2 hours, resulting in a 40 μm thick inner layer with a filtration efficiency of only 88%.

[0033] Example 5

[0034] PVDF nanofiber membranes were prepared using an electrospinning device. The spinning dope concentration was 15%, the spinning voltage was 30 kV, the syringe speed was 2.0 mL / min, the receiving roller speed was 300 rpm, and the receiving distance was 20 cm. The web layup time was 4 hours, and the nanofiber membrane had a thickness of 40 μm and a filtration efficiency of 93%.

[0035] Example 6

[0036] PVDF nanofiber membrane was prepared by spinning using electrospinning equipment.

[0037] When preparing the surface layer, the spinning parameters were controlled as follows: spinning solution concentration of 15%, spinning voltage of 15 kV; injector speed of 3.0 mL / min; receiving roller speed of 100 rpm; receiving distance of 20 cm, and web laying time of 3 h.

[0038] When preparing the inner layer, the spinning parameters were controlled as follows: spinning solution concentration of 8%, spinning voltage of 30 kV; injector speed of 5.0 mL / min; receiving roller speed of 300 rpm; receiving distance of 30 cm, and web laying time of 4 h.

[0039] A PVDF nanofiber membrane with a gradient structure was prepared.

[0040] The appearance of its surface and inner layers is as follows Figure 1 、 Figure 2As shown, it can be seen that the surface fiber diameter and membrane pore size are both larger than the inner fiber diameter and membrane pore size, among which the surface fiber diameter is greater than 0.48μm, and the inner layer is less than 0.48μm, the membrane pore size of the surface layer is greater than 2μm, and the inner layer is less than 2μm, the average fiber diameter of the PVDF nanofiber membrane is 0.48μm, and the overall thickness is about 40μm.

[0041] The nanofiber membrane was used to filter liquids containing SiO2 particles with a particle size of 500nm and liquids containing SiO2 particles with a particle size of 80nm. The filtration efficiency was very excellent, reaching up to 99.77%, meeting the requirements of high-precision filtration. Compared with a single surface fiber membrane or a single inner fiber membrane, the filtration efficiency of the nanofiber membrane was significantly improved at the same thickness. In addition, the method of the present invention was used to repeatedly prepare PVDF gradient structure nanofiber membranes, and the liquids containing particulate matter at different concentrations (0.0006-0.001g / mL) and different pressure differences (0.02-0.04MPa) were filtered. The membranes showed high filtration efficiency, and the actual filtration effect was very consistent with the effect obtained by model calculation. The fiber membrane obtained by the method of the present invention has a high-precision purification effect on particulate matter in the liquid (see Figures 3 to 6 ).

[0042] The embodiments described above are merely some preferred embodiments of the present invention and are not intended to limit the present invention. Persons skilled in the art may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, any technical solution obtained by equivalent substitution or equivalent transformation falls within the scope of protection of the present invention.

Claims

1. A method for preparing a gradient structure nanofiber membrane material with high-precision purification effect, characterized in that: PVDF nanofiber membrane is prepared by electrospinning. The PVDF nanofiber membrane obtained by regulating the spinning parameters during the spinning process has a double-layer composite gradient structure. The double-layer composite gradient structure includes a surface layer for first contacting the liquid to be purified and an inner layer connected to the surface layer for outputting the purified liquid. The nanofiber diameter and fiber membrane pore size in the surface layer are both larger, while the nanofiber diameter and fiber membrane pore size in the inner layer are both smaller, thereby forming a double gradient of fiber diameter and fiber membrane pore size in the PVDF nanofiber membrane.

2. The method for preparing a gradient structure nanofiber membrane material with high-precision purification effect according to claim 1, characterized in that: The electrospinning solution is a mixed solvent of tetrahydrofuran (THF) and dimethylformamide (DMF), the mass ratio of THF to DMF is 1:1, and the mass concentration of PVDF in the spinning solution is 8-15%.

3. The method for preparing a gradient structure nanofiber membrane material with high-precision purification effect according to claim 1, characterized in that: The spinning parameters include spinning solution concentration, spinning voltage, syringe speed, receiving roller speed, receiving distance and fiber web stacking time. By regulating these spinning parameters of the surface layer and the inner layer, the fiber diameter, pore size and thickness of the surface layer and the inner layer nanofiber membrane are controlled to present a precise gradient distribution structure.

4. The method for preparing a gradient structure nanofiber membrane material with high-precision purification effect according to claim 1, characterized in that: When preparing the surface layer, the spinning parameters are controlled as follows: the spinning solution concentration is 12-15%, the spinning voltage is 15-20kV; the injector speed is 1.0-3.0mL / min; the receiving roller speed is 100-200 rpm; the receiving distance is 10-20cm, and the fiber web laying time is 2-3h; when preparing the inner layer, the spinning parameters are controlled as follows: the spinning solution concentration is 8-11%, the spinning voltage is 20-30kV; the injector speed is 4.0-5.0mL / min; the receiving roller speed is 200-300 rpm; the receiving distance is 20-30cm, and the fiber web laying time is 3-4h.

5. The method for preparing a gradient structure nanofiber membrane material with high-precision purification effect according to claim 1, characterized in that: The average diameter of the PVDF nanofiber membrane is 0.45 to 0.5 μm, and the overall thickness is 38 to 42 μm.

6. The method for preparing a gradient structure nanofiber membrane material with high-precision purification effect according to claim 1, characterized in that: The fiber diameter of the surface layer of the PVDF nanofiber membrane is greater than 0.48 μm, and the fiber membrane diameter of the inner layer is less than 0.48 μm; the membrane pore size of the surface layer is greater than 2 μm, and the membrane pore size of the inner layer is less than 2 μm; the thickness of the surface layer is 19-21 μm, and the thickness of the inner layer is 19-21 μm.

7. A gradient structure nanofiber membrane material with high-precision purification effect, characterized in that: The method is prepared by the method according to any one of claims 1 to 6.

8. A liquid filtration membrane for use in semiconductor manufacturing processes, characterized in that: Containing the material as claimed in claim 7.

Images