CN102305256B - Metal micrometer/nanometer spring as well as preparation method and application thereof - Google Patents

Abstract

The invention belongs to the technical field of micro-nano devices, in particular to a metal micro/nano spring and its preparation method and application. The preparation method includes: preparing a substrate, and there is a sacrificial layer on the substrate; depositing a metal strip with internal stress and anisotropic Young's modulus on the sacrificial layer; selectively removing the metal strip between the metal strip and the substrate. part of the sacrificial layer, the metal strip is released, so that the metal strip curls into a metal nano/micro spring. The metal nano/micro spring can be used for the measurement of the flow sensor, specifically, the substrate with the metal micro/nano spring is fixed inside the fluid channel; when the fluid flows through the channel, the spring reaches an equilibrium state, and the elongation of the spring is measured volume to measure fluid velocity.

Description

A kind of metal micro/nano spring and its preparation method and application

technical field

The invention belongs to the technical field of micro-nano devices, and in particular relates to a metal micro/nano spring and its preparation method and application.

Background technique

In recent years, micro-nano devices, such as micro-nano-scale tubes, wires, and springs, have attracted extensive attention due to their potential applications in drug delivery, sensors, optics, and hydrogen storage. Among all three-dimensional micro-nano devices, springs have been more extensively studied due to their special morphology. Due to the unique helical structure of the micro/nano spring and the piezoelectric, mechanical and electrical properties of the material itself, this micro/nano spring is widely used in micro-nano electromechanical systems (N/MEMS), drug delivery and cell There are potential applications in areas such as manipulation. Due to the high specific surface area and easily modifiable surface of nanofilms, the micro/nanosprings obtained by curling nanofilms also have certain application prospects in biological and chemical sensors.

In 2006, Pu XianGao et al. used a solid-gas process to successfully prepare a superelastic ZnO nanospring. Cao Chuanbao et al. prepared a superelastic Si ₃ N ₄ micron spring by vapor phase chemical deposition in 2007. Li Zhang et al. successfully prepared micro-springs by curling a semiconductor double-layer film with internal stress. In the method adopted by Li Zhang et al., the internal stress of the bilayer film is caused by the lattice mismatch between the different layers, and the direction of curling is determined by the Young's modulus, while in the semiconducting film the Young's modulus has significant anisotropy. Their results show that the diameter of the spring is determined by the thickness of the film and the degree of lattice mismatch, while the curling direction is along the direction of the smallest Young's modulus.

At present, micron/nanosprings prepared by curling nanofilms are generally semiconductor epitaxial materials, such as InGaAs/GaAs double-layer films and SiGe/Si double-layer films. / Research report on the preparation of nano springs. Compared with semiconductor materials, metal materials have better mechanical and electrical properties, so metal micro/nano springs are more suitable for application in micro-nano devices.

Contents of the invention

The object of the present invention is to provide a metal micro/nano spring with excellent mechanical and electrical properties and its preparation method and application.

The preparation method of the metal micro/nanospring provided by the invention comprises the following steps:

(1) Prepare a substrate on which a sacrificial layer exists;

(2) Depositing metal strips with internal stress and anisotropic Young's modulus on the sacrificial layer;

(3) Selectively remove part of the sacrificial layer between the metal strip and the substrate to release the metal strip, so that the metal strip curls into a metal nano/micro spring. the

In the present invention, step (2) deposits a metal strip with internal stress and anisotropic Young's modulus on the sacrificial layer, including the following two steps, first depositing a layer on the sacrificial layer by physical or chemical vapor deposition The metal film is then patterned by photolithography, called metal strips. Among them, physical vapor deposition methods include sputtering, thermal evaporation, and electron beam evaporation.

In the present invention, the physical vapor deposition method is used to deposit a layer of metal thin film on the sacrificial layer, by controlling deposition parameters, such as deposition rate, substrate temperature, substrate tilt angle and deposition pressure, etc., to obtain Stress Gradient Difference and Anisotropic Young's Modulus of Metal Thin Films.

In the present invention, the geometric parameters of the metal micro/nano spring, such as diameter, helix angle and pitch, are determined according to design requirements.

In the present invention, the material of the metal micro/nanospring (deposited metal thin film) can be a single component metal (metal thin film) such as gold, titanium, chromium, or aluminum, or an alloy of these metals (alloy thin film) , It can also be a multilayer metal (multilayer metal film) of these metals.

In the present invention, the sacrificial layer may be a SiO2 layer.

The metal micron/nanospring provided by the present invention can be used in the flow sensor to measure the flow rate and flow rate, as follows:

The flow sensor consists of a fluid channel inside which a substrate with metallic micro/nanosprings is held. When the fluid passes through the channel, the spring is in a balanced state due to the viscous force of the fluid flow and the tension of the substrate to the spring. At this time, the viscous force is numerically equal to the tension force of the substrate on the spring. The viscous force is related to the viscosity coefficient of the fluid itself and the flow velocity, while the tension of the substrate on the spring can be expressed by the elongation of the spring. Generally speaking, for the same fluid, its viscosity coefficient is fixed, and the elongation of the spring increases with the flow rate of the fluid. Therefore, we can measure the flow rate of the fluid by measuring the elongation of the spring. The elongation of the spring is measured by optical microscopy.

Description of drawings

Fig. 1 is a flowchart of the preparation of metal micro/nano springs in the present invention. Among them, (a) means that there is a layer of SiO ₂ on the Si substrate as a sacrificial layer; (b) means that a layer of Au film with a thickness of 40 nm is deposited on the SiO ₂ sacrificial layer by electron beam evaporation; (c) means that using Hydrofluoric acid removes the _SiO2 sacrificial layer; (d) finally forms Au micro/nano springs.

Fig. 2 is a graph showing the anisotropic Young's modulus of the Au film obtained by depositing the film at an inclined substrate angle.

Fig. 3 is a schematic diagram of testing fluid flow rate using metal micro/nano springs. Among them, (a) is the initial state of the spring when the fluid is still, and (b) is the state of the spring being elongated by the viscous force when the fluid flows from left to right at a certain speed.

Labels in the figure: 1. Substrate; 2. Sacrificial layer; 3. Metal layer; 4. Metal micro/nano spring; 5. The angle between the normal direction of the substrate and the incident direction of the evaporated atomic gas; 6. Evaporation source ; 7. Substrate; 8. Fluidic channel.

Detailed ways

The present invention is further described by examples below.

In the following, the preparation of metal micro/nano springs by the invention will be further described in conjunction with the accompanying drawings and specific examples.

Fig. 1 is a schematic diagram of preparing gold micro/nanosprings using the method of the present invention. Among them, (a) is a layer of SiO ₂ on the Si substrate 1 as the sacrificial layer 2 . (b) shows that an Au metal layer 3 with a thickness of 40 nm was deposited on the SiO ₂ sacrificial layer by electron beam evaporation. Wherein, in the deposition process, by changing the deposition parameters, such as deposition rate, substrate temperature and deposition pressure, etc., an Au film with internal stress can be prepared; At a certain angle 5 , as shown in Figure 2, due to the shadow effect of the deposited film at an inclined substrate angle, the Au film deposited by this method has anisotropic Young's modulus. Then use photolithography to pattern the Au thin film to obtain metal strips, as shown in (c). Finally, the SiO ₂ sacrificial layer was removed by hydrofluoric acid, so that the Au metal strips were separated from the substrate to form Au metal micro/nano springs 4, as shown in (d).

3 is a schematic diagram of testing fluid flow rate based on metal micro/nano springs. The substrate 7 with metal micro/nano springs is fixed inside the fluid channel 8, and one end of the metal micro/nano springs 4 is fixed on the substrate 7. Among them, (a) means that when the fluid is still, the spring is in the initial state without being stretched, and the length at this time is l ₀ . (b) means that when the fluid flows through at a certain speed, the spring receives the action of viscous force and elongates, and the length at this time is l . The elongation x of the spring is equal to l - l ₀ , which is determined by the viscosity coefficient of the fluid and the flow rate. When using the same fluid, the viscosity coefficient remains unchanged, so the x value is only proportional to the flow rate. Therefore, according to the above analysis, the flow rate of the fluid can be measured by measuring the elongation of the spring.

Claims (6)

1. the preparation method of a metal micrometer/nanometer spring is characterized in that concrete steps are:

(1) prepare a substrate, have sacrifice layer on substrate;

(2) metal bar that deposition has internal stress and anisotropic Young's modulus on sacrifice layer;

(3) optionally remove partial sacrifice layer between metal bar and substrate, discharge metal bar, thus the curling metal nano/micron spring that becomes of metal bar;

Step (2) deposits the metal bar with internal stress and anisotropic Young's modulus on sacrifice layer, comprise following two steps, at first utilize physics or Low Pressure Chemical Vapor Deposition to deposit the layer of metal film on sacrifice layer, then utilize the method for photoetching with metal thin-film pattern, obtain metal bar.

2. preparation method according to claim 1, it is characterized in that the described physical vaporous deposition that utilizes deposits the layer of metal film on sacrifice layer, by controlling deposition parameter, comprise deposition rate, underlayer temperature, substrate tilting angle or deposition pressure, obtain having poor in direction of growth internal stress gradient and the metallic thin film anisotropy Young's modulus.

3. preparation method according to claim 1 and 2 is characterized in that the material of described metal is gold, titanium, chromium or aluminium one-component metal, or several alloy in these metals, or several multiple layer metal in these metals.

4. preparation method according to claim 1 and 2, is characterized in that described sacrifice layer is SiO ₂Layer.

5. the metal micrometer/nanometer spring for preparing of preparation method as described in one of claim 1-4.

6. metal micrometer/nanometer spring as claimed in claim 5 is measured the application of rate of flow of fluid and flow in flow transducer.

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