CN115477276A - Preparation method and application of convex mold for mixed-scale nanofluidic chip - Google Patents

Abstract

The invention discloses a preparation method and application of a convex die for a mixed-scale nanofluid chip, wherein the method comprises the following processing steps: firstly, etching a monocrystalline silicon sample by adopting micro-nano etching equipment, and then putting the monocrystalline silicon sample into a mixed solution of silane and ethanol to ensure that silane molecules are fully adsorbed in an etching area; then selectively etching the monocrystalline silicon sample by adopting an etching solution to etch a silicon convex structure with micron-level height and centimeter-level length; and then, etching the surface of the monocrystalline silicon with the silicon convex structure by adopting micro-nano etching equipment, and then selectively etching again to form the convex structure with the nano-scale height so as to finish the processing of the mixed-scale nano-convex mold structure. The invention realizes the integrated processing of the male die with the mixed scale characteristic on the surface of the monocrystalline silicon by utilizing the twice scanning probe technology, has simple processing flow and low cost, and can improve the production efficiency of the nanofluid chip.

Description

Preparation method and application of convex mold for mixed-scale nanofluidic chip

technical field

The invention relates to the technical field of micro-nano processing, in particular to a preparation method and application of a convex mold for a mixed-scale nanofluid chip.

Background technique

Nanofluidics is an emerging science that studies the properties and applications of fluids in and around channels with one or more dimensions not exceeding 100 nm. The interaction of surface/interface forces plays an important role in the fluid transport in nanochannels, and there are some unique chemical and physical phenomena in nanochannels, such as electric double layer overlapping, ion concentration polarization, and nanofluidic rectification, etc. These properties facilitate the application of nanofluidic devices, including diodes and ion field-effect transistors, in single-molecule analysis, biochemical detection, energy harvesting, and DNA sequencing.

Nanofluidic devices typically require a network of microfluidic channels as pathways to guide target molecules into the nanochannels. A combination of microfabrication and nanofabrication processes is usually employed to fabricate nanofluidic chips with mixed-scale features (generally spanning nm to cm scales). However, conventional micro/nanofabrication methods for fabricating mixed-scale nanofluidic chips, namely photolithography, electron beam/focused ion beam lithography, and nanoimprint lithography, face great challenges in fabricating cross-scale structures. Therefore, the development of a simple and low-cost integrated method for processing mixed-scale convex molds is crucial for the mass production of nanofluidic chips.

Contents of the invention

The purpose of the present invention is to address the above problems, and provide a method for preparing a convex mold for mixed-scale nanofluidic chips and its application. The method uses scanning probe technology to realize the integration of convex molds with mixed-scale features on the surface of single crystal silicon processing, the processing flow is simple and the cost is low, and the prepared convex mold is very suitable for the mass production of nanofluidic chips.

To achieve the above object, the present invention adopts the following technical solutions:

A method for preparing a convex mold for a mixed-scale nanofluidic chip, the processing steps of which are as follows:

S1. Use micro-nano scribing equipment to perform the first scribing process on the surface of the clean single crystal silicon sample according to the predetermined trajectory;

S2. Put the monocrystalline silicon sample after the first scribing in step S1 into the mixed solution to soak, so that the silane molecules are fully adsorbed on the scribing area, so as to improve the ability of the scribing area to resist etching; the mixed solution It is a mixture of silane and ethanol, or a mixture of siloxane and ethanol; the soaking time is 1-3h;

S3, using an etching solution to selectively etch the single crystal silicon sample processed in step S2, so as to etch a silicon convex structure with a micron-level height and a centimeter-level length;

S4. Use micro-nano scribing equipment 2 to perform a second scribing on the single crystal silicon surface having a silicon convex structure in step S3, and form nanoscale scratches on the single crystal silicon surface, and the nanoscale scratches are continuous structures ;

S5, immersing the monocrystalline silicon sample obtained in step S4 again into an etching solution for selective etching, thereby forming a convex structure with a nanoscale height, and then completing the integrated processing of the mixed-scale convex mold structure.

In step S1, the contact pressure used for scribing by the micro-nano scribing device is 11-20 GPa, and the speed is 0.1-1 mm/s.

In step S2, the silane or siloxane can be: 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane (PFDS), octadecyltrichlorosilane (OTS) or polydimethyl Siloxane (PDMS), etc., which are used to improve the ability of wet etching masks.

In step S3, the etching solution adopts potassium hydroxide solution (mass concentration is 20%) or tetramethylammonium hydroxide solution (mass concentration is 25%); the etching solution in step S5 adopts potassium hydroxide solution (mass concentration 20%).

In step S4, the micro-nano scribing device 2 performs the second scribing with a contact pressure of 11-13 GPa and a speed of 1-100 μm/s, the purpose of which is to form nanoscale scratches.

Further, the scribing area radius of the first micro-nano scribing device is larger than that of the second micro-nano scribing device.

Further, the first micro-nano scribing device and the second micro-nano scribing device use different diamond probes. Wherein, the area radius of the diamond probe 1 as the micro-nano scribing device 1 is in micron order, and the area radius of the diamond probe 2 as the micro-nano scribing device 2 is 20-50 nm.

Further, the etching time in the step S3 is 25-35 min, and the temperature of the etching solution is 40-50°C.

Further, the etching time in the step S5 is 2-4 min, and the temperature of the etching solution is 22-28°C.

Furthermore, combined with nano-transfer printing technology, the mixed-scale convex mold structure obtained in step S5 can be transferred to the surface of polydimethylsiloxane (PDMS), polymethyl methacrylate (PMMA) and other materials to achieve mixed-scale nano Mass production of fluidic chips.

The beneficial effects of the present invention are as follows:

The invention utilizes the mixed solution of silane and ethanol to make silane fully adsorbed on the scribed area, which improves its ability to resist etching, and can better selectively etch the preliminary mixed-scale features of centimeter-level length and micron-level height ;During the second selective etching, the convex structure with nanoscale height is obtained; The convex mold structure with mixed-scale features; generally speaking, the present invention realizes the integrated processing of convex molds with mixed-scale features on the surface of single crystal silicon, and has a simple process and low cost, and is very suitable for the production of nanofluidic chips.

Description of drawings

Fig. 1 is a schematic diagram of the processing flow of the present invention.

Fig. 2 is a schematic diagram of the real object of convex mold processing with mixed-scale features realized by the present invention.

detailed description

The present invention will be described in detail below through specific embodiments in conjunction with the accompanying drawings.

Example 1

As shown in Figure 1, in this embodiment, the method for preparing a convex mold for a mixed-scale nanofluidic chip includes the following steps:

S1. Using micro-nano scribing equipment-carry out scribing processing on the clean single crystal silicon surface according to the predetermined trajectory, and the scribing motion trajectory is carried out according to the surface scanning mode, exposing the single crystal silicon substrate in the scribed area;

The radius of curvature of the selected micro-nano scribing device 1 is about 10 μm, and the scribing load is 20-50 mN.

S2. Put the monocrystalline silicon sample after the first scoring into a mixed solution of 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane and ethanol (excellent grade), soak for 2 hours, and make the silane Molecules are fully adsorbed in the scribed area, thereby improving the masking ability of the scribed area.

S3. Using a potassium hydroxide solution to selectively etch the monocrystalline silicon sample treated in step S2, thereby etching a silicon convex structure with a micron-level height and a centimeter-level length; the selected etching time is about 30 min, The etchant temperature was maintained at 40°C.

S4. On a scanning probe microscope or scratch instrument, use micro-nano scribing equipment 2 to scribble the single crystal silicon surface with silicon convex structure in step S3.

S5. Immerse the monocrystalline silicon sample obtained in step S4 again in a potassium hydroxide solution for selective etching. The selected etching time is 3 min, and the temperature of the etchant is kept at 26° C., thereby forming a nanoscale height. structure, and then complete the integrated processing of the mixed-scale convex die structure.

Example 2

In this embodiment, the method for preparing a convex mold for a mixed-scale nanofluidic chip includes the following steps:

S1. Using micro-nano scribing equipment-carry out scribing processing on the clean single crystal silicon (100) surface according to the predetermined trajectory, and the scribing motion trajectory is carried out according to the surface scanning mode, exposing the single crystal silicon substrate in the scribed area;

The micro-nano scribing device uses a contact pressure of 11-17 GPa and a speed of 0.1-1 mm/s when scribing.

S2. Put the monocrystalline silicon sample after the first scoring into a mixed solution of octadecyltrichlorosilane (OTS) and ethanol, and soak for 1.5 hours, so that the silane molecules are fully adsorbed on the scoring area, thereby improving the marking efficiency. The masking ability of the designated area;

S3. Using tetramethylammonium hydroxide solution to selectively etch the monocrystalline silicon sample treated in step S2, thereby etching a silicon convex structure with a micron-level height and a centimeter-level length; the selected etching time is about 33 min, the etchant temperature is kept at 45-50°C;

S4. On a scanning probe microscope or scratch instrument, use micro-nano scribing equipment 2 to scribe the single crystal silicon surface with a silicon convex structure in step S3;

S5. Immerse the monocrystalline silicon sample obtained in step S4 again in a potassium hydroxide solution for selective etching, thereby forming a convex structure with a nanoscale height. The selected etching time is 2 min, and the temperature of the etchant is kept at 22 ℃, and then complete the integrated processing of the mixed-scale convex mold structure.

Example 3

In this embodiment, the method for preparing a convex mold for a mixed-scale nanofluidic chip includes the following steps:

S1. Using micro-nano scribing equipment-carry out scribing processing on the clean single crystal silicon (100) surface according to the predetermined trajectory, and the scribing motion trajectory is carried out according to the surface scanning mode, exposing the single crystal silicon substrate in the scribed area;

The micro-nano scribing device uses a contact pressure of 16-20 GPa and a speed of 0.1-1 mm/s when scribing.

S2. Put the monocrystalline silicon sample after the first marking into a mixed solution of polydimethylsiloxane (PDMS) and ethanol, soak for 2 hours, so that the silane molecules are fully adsorbed on the marking area, thereby improving the marking Area masking capabilities;

S3. Selectively etch the monocrystalline silicon sample treated in step S2 with a potassium hydroxide solution, thereby etching a silicon convex structure with a micron-level height and a centimeter-level length; the selected etching time is about 25 min, The etchant temperature is kept at 48°C;

S4. On a scanning probe microscope or scratch instrument, use micro-nano scribing equipment 2 to scribe the single crystal silicon surface with a silicon convex structure in step S3;

S5. Immerse the monocrystalline silicon sample obtained in step S4 again in a potassium hydroxide solution for selective etching, thereby forming a convex structure with a nanoscale height. The selected etching time is 3 minutes, and the temperature of the etchant is kept at 28° C. , and then complete the integrated processing of the mixed-scale convex die structure.

Example 4

For any one of the above-mentioned embodiments 1-3, the radius of the scribed area of the micro-nano scribing device 1 used is larger than that of the micro-nano scribing device 2 .

Wherein, the first micro-nano scribing device and the second micro-nano scribing device use diamond probes with different radii.

Specifically, the area radius of the diamond probe 1 as the micro-nano scribing device 1 is 8-12 μm, and the area radius of the diamond probe 2 as the micro-nano scribing device 2 is 20-50 nm.

The convex mold of the mixed-scale nanofluidic chip prepared by any of the above-mentioned embodiments is shown in FIG. 2 .

Furthermore, combined with nano-transfer printing technology, the mixed-scale convex mold structure obtained in step S5 can be transferred to the surface of polydimethylsiloxane (PDMS), polymethyl methacrylate (PMMA) and other materials, so that the mixed-scale Mass production of nanofluidic chips.

Claims (10)

1. The preparation method of the convex mold that is used for mixed-scale nanofluidic chip is characterized in that, processing steps are as follows: S1. Using micro-nano scribing equipment-carry out the first scribing process on the surface of the clean single crystal silicon sample according to the predetermined trajectory, exposing the single crystal silicon substrate in the scribed area; S2. Put the monocrystalline silicon sample after the first scribing in step S1 into the mixed solution to soak, so that the silane molecules are fully adsorbed on the scribing area, so as to improve the etching resistance of the scribing area; the mixing The solution is a mixture of silane and ethanol, or a mixture of siloxane and ethanol; the soaking time is 1-3h; S3, using an etching solution to selectively etch the single crystal silicon sample processed in step S2, so as to etch a silicon convex structure with a micron-level height and a centimeter-level length; S4. Using micro-nano scribing equipment 2 to perform a second scribing on the surface of the single crystal silicon having a silicon convex structure in step S3, forming nanoscale scratches on the surface of the single crystal silicon; S5, immersing the monocrystalline silicon sample obtained in step S4 again into an etching solution for selective etching to form a convex structure with a nanoscale height, and obtain a mixed-scale convex mold structure. 2. The method for preparing a convex mold for mixed-scale nanofluidic chips according to claim 1, characterized in that: in step S1, the contact pressure used when the micro-nano scribing device is scored is 11-20 GPa. 3. The method for preparing a convex mold for mixed-scale nanofluidic chips as claimed in claim 1, characterized in that: in step S2, the silane or siloxane adopts: 1H, 1H, 2H, 2H-perfluoro Decyltriethoxysilane, Octadecyltrichlorosilane or Dimethicone. 4. The method for preparing a convex mold for mixed-scale nanofluidic chips as claimed in claim 1, characterized in that: the etching solution in step S3 adopts a potassium hydroxide solution with a mass concentration of 20% or a mass concentration of 25%. % tetramethylammonium hydroxide solution; the etching solution in step S5 is a potassium hydroxide solution with a mass concentration of 20%. 5. The method for preparing a convex mold for mixed-scale nanofluidic chips according to claim 1, characterized in that: in step S4, the contact pressure used when marking the second micro-nano scribing device is 11-13 GPa, speed 1-100 μm/s. 6. The method for preparing a convex mold for a mixed-scale nanofluidic chip as claimed in claim 1, wherein the radius of the marking area of the first micro-nano marking device is greater than that of the second micro-nano marking device; The first micro-nano scribing device adopts the first diamond probe with an area radius of micron; the second micro-nano scribing device adopts the second diamond probe with an area radius of 20-50 nm. 7. The method for preparing a convex mold for a mixed-scale nanofluidic chip as claimed in claim 1, wherein: the radius of the marking area of the micro-nano scribing device one is greater than that of the micro-nano scribing device two; Micro-nano scribing equipment 1 and micro-nano scribing equipment 2 both use atomic force microscopes, which are used to scribe and form nanoscale scratches. 8. the preparation method of the convex mold that is used for mixed-scale nanofluid chip as claimed in claim 1 is characterized in that: the etching time is 25-35 min in the described S3 step, and the temperature of etching solution is 40-50 ℃. 9. the preparation method of the convex mold that is used for mixed-scale nanofluid chip as claimed in claim 1, is characterized in that: in the described S5 step, etching time is 2-4 min, and the temperature of etching solution is 22-28 ℃. 10. The application of the convex mold for mixed-scale nanofluidic chips prepared by claim 1 is characterized in that: using nano-transfer printing technology, the mixed-scale convex mold structure obtained in step S5 is transferred to polydimethylsiloxane The surface of alkane or polymethyl methacrylate is used to fabricate mixed-scale nanofluidic chips.

Images