CN117012541B - Controllable stripping preparation method of high-density flexible micro-nano coil - Google Patents

Abstract

The invention belongs to the technical field of inductors and coils, and in particular relates to a controllable peeling preparation method of high-density flexible micro-nano coils, which solves the technical problems in the background technology. It includes preparing a rigid silicon substrate and pasting polyimide on the upper surface. Tape, make a single-layer MEMS micro-nano coil on the polyimide tape, and then spin-coat the photosensitive polyimide film; repeat making the coil and spin-coating the photosensitive polyimide film until the total number of coil layers reaches the requirement ; Finally, a photosensitive polyimide film as a stress insulation layer is spin-coated on the top layer for encapsulation; the entire finished product is soaked in an acetone solution, and after a certain period of time, the entire multi-layer micro-nano coil is peeled off from the rigid silicon substrate to obtain a flexible micro-nano coil. nanocoil. The polyurethane glue on the lower surface of the polyimide tape reacts with the organic solvent acetone to reduce the adhesive force of the tape. The tensile stress of the stress insulation layer drives the film layer structure to produce split fractures to promote controlled peeling, and finally achieves the effect of controlled peeling. .

Description

A controlled peeling preparation method for high-density flexible micro-nano coils

Technical field

The invention relates to the technical fields of inductors and coils, and in particular to a controllable peeling preparation method of high-density flexible micro-nano coils.

Background technique

With the continuous development of the field of microelectronics, flexible micro-nano devices have received widespread attention due to their excellent electrical properties and simple and low-cost manufacturing processes. The combination of MEMS micro-nano coil manufacturing technology and micro-energy harvesting technology and many wearable flexible devices It has more and more extensive application prospects.

Flexible micro-nano coils can greatly increase the power density of devices, reduce size and facilitate integration. However, since MEMS micro-nano coils are always prepared on rigid silicon substrates, the disadvantage is that when the number of coil turns is high, they are bulky, which is not conducive to use in limited space and conformal assembly in complex structures. , in flexible electronic devices, it cannot be peeled off from the rigid silicon substrate, which greatly limits its application; or MEMS micro-nano coils are directly produced on the flexible substrate. The disadvantage is that bending and condensation phenomena occur easily during the production process. , causing damage to the MEMS micro-nano coil. Therefore, the complete controllable peeling of MEMS micro-nano coils is still an urgent problem to be solved. Therefore, developing a simple and feasible high-density micro-nano coil controllable peeling method is suitable for MEMS electromagnetic micro-energy harvesting devices and many wearable flexible devices. The high-performance output is crucial and is of great significance to the development of the Internet of Things and flexible electronics.

Currently, there are two methods to achieve controllable peeling of MEMS micro-nano coils. One is to effectively separate the film from the silicon substrate through laser irradiation; the other is to completely separate the film from the silicon substrate through chemical etching and successfully transfer it to a flexible substrate. However, the disadvantages of laser peeling are that the operation is complicated and the temperature generated during laser irradiation is so high that the laser may damage the film during irradiation. Moreover, this method is costly and cannot be widely used. The disadvantage of another chemical etching method is that it requires multiple UV lithography and wet etching processes, which to a certain extent will destroy the structure of the micro-nano coil and affect the performance output of the micro-nano coil film, thereby limiting the micro-nano coil The performance of power generation.

Contents of the invention

In order to overcome the technical defects of difficult peeling such as incomplete peeling in existing controllable peeling preparation methods of MEMS micro-nano coils, the present invention provides a controllable peeling preparation method of high-density flexible micro-nano coils.

The invention provides a controllable peeling preparation method of high-density flexible micro-nano coils, which includes the following steps:

Step 1: Prepare a rigid silicon substrate and clean the rigid silicon substrate;

Step 2: Paste polyimide tape on the upper surface of the rigid silicon substrate in step 1. The polyimide tape uses polyurethane glue, and then clean the surface of the polyimide tape;

Step 3: Make a single-layer MEMS micro-nano coil on the polyimide tape on top of the rigid silicon substrate, then spin-coat the photosensitive polyimide film, and photolithography and MEMS micro-nano coils on the photosensitive polyimide film The through holes corresponding to the two electrodes of the coil;

Step 4. Repeat Step 3 until the total number of layers of MEMS micro-nano coils reaches the design requirements;

Step 5: Finally, spin-coat the photosensitive polyimide film as the stress insulation layer on the top layer for packaging, and photoetch through holes corresponding to the two electrodes of the MEMS micro-nano coil on the stress insulation layer;

Step 6: Soak the entire finished product obtained in Step 5 in the acetone solution. After a certain period of time, peel off the entire multi-layer MEMS micro-nano coil from the interface between the polyimide tape and the rigid silicon substrate to obtain a flexible micro-nano coil.

The cleaning process is to provide a flat surface for subsequent processes, and the polymer polyimide is spin-coated on the stripped device. Polyimide is a macromolecule composed of repeating structural units. These subunits are connected through covalent chemical bonds. The polyurethane glue on the polyimide tape is a kind of formate, which is a macromolecular compound containing repeating urethane groups in the main chain. It is composed of organic diisocyanate or polyisocyanate and dihydroxy or polyhydroxy compounds. Made by addition. From the perspective of molecular structure, the groups connected by -O- are all polar, and acetone is also a polar molecule. It can be dissolved in acetone through the principle of "similarity dissolves". Acetone is a commonly used solvent that dissolves polyurethane with a purely linear molecular structure. Polyurethane is a macromolecular compound containing repeating urethane groups in its backbone. In addition, acetone can also form a liquid interface layer on the surface of the polyimide tape to separate the adhesive part of the tape surface from the base material, increasing the convenience of tape detachment. By using its tensile stress to drive the film layer structure to generate cleavage fractures and propagate along the specified interface, complete and high-quality peeling of the flexible coil can be achieved. The polymer photosensitive polyimide film is not only a stress layer, but also plays an encapsulating role to protect double-layer coils or even multi-layer coils. The main function of the top layer of photosensitive polyimide film is to improve the corrosion resistance and mechanical properties of the parts. Through the controlled peeling preparation method of flexible micro-nano coils according to the present invention, the quality and integrity of flexible micro-nano coils will be greatly improved.

Preferably, in step one and step two, the cleaning treatment is performed using deionized water and nitrogen.

Preferably, in step two, place the rigid silicon substrate on the workbench of the laminating machine, use the heating function of the laminating machine to heat the rigid silicon substrate to 80°C to remove water vapor, and at the same time open the vacuum valve of the workbench of the laminating machine to proceed. Use vacuum to adsorb the rigid silicon substrate to the workbench of the laminating machine, and then paste the polyimide tape onto the rigid silicon substrate. Removing water vapor can effectively prevent bubbling under the polyimide tape during subsequent film application. The rigid silicon substrate is adsorbed to the workbench of the film application machine by vacuuming to prevent the rigid silicon substrate from moving. This ensures that there are no bubbles and the surface is free of bubbles during the film application process. smooth.

Preferably, in step three, before making a single-layer MEMS micro-nano coil, the adhesion layer and the seed layer are sputtered on the surface of the polyimide tape. The thickness ratio of the adhesion layer and the seed layer is 1:5 or 1:10. , the adhesion layer and the seed layer as a whole serve as a conductive layer. The adhesion layer and the conductive layer may be a chromium layer and a copper layer, a chromium layer and a gold layer, or a titanium layer and a copper layer, respectively.

Preferably, the sub-steps for making a single-layer MEMS micro-nano coil are:

S1. Place the rigid silicon substrate with the conductive layer on the workbench of the glue leveling machine and spin-coat the photoresist. When the photoresist reaches the set thickness, use a photolithography machine to perform photolithography exposure patterning processing, and then Process with developer, use a plasma remover to remove residual photoresist, and finally harden the film on a high-temperature baking table. The first layer of coil template is prepared;

S2. Dip the acetone solution and wipe the ten electrode interfaces evenly in the circumferential direction of the rigid silicon substrate. Connect the power clips to the opposite set of electrode interfaces to perform electroplating treatment on the first layer coil template. After a certain period of time, switch to the next set of opposite electrode interfaces. The electrode interfaces are connected in turn until the entire single-layer coil is prepared.

Compared with the existing technology, the technical solution provided by the present invention has the following advantages: the present invention proposes a simple, efficient and economical method to controllably peel off flexible micro-nano coils, and use polyimide tape, that is, industrial grade polyimide film When pasted on a silicon wafer as the base, the silicon wafer is used as the hard base, the polyimide film is used as the controllable peelable flexible base film, and the micro-nano coil device is produced on top; compared with the traditional electroplating coating, the photosensitivity As a stress layer, the polyimide film has less stress and is less likely to cause deformation of parts or damage to devices. This is particularly important for flexible coil micro-nano processes; at the same time, the uniformity of the coating is achieved by adjusting process parameters to ensure the thickness of the coating. The consistency and stability of the protective performance can further ensure the service life of the parts; the controllable peeling of the flexible micro-nano coils first spin-coates polyimide polymers of different thicknesses on the top of the device as a stress layer, and its tensile stress drives the film layer The structure generates split fractures to promote controlled peeling. After the stress layer is cured, the entire device is placed in an acetone solution. The polymers of the polyurethane glue (polyisocyanate and polyol ether) on the lower surface of the polyimide tape are easy to react with organic solvents. Acetone (ketone substance) reacts, thereby reducing the interaction force between the polyimide tape and the silicon wafer, reducing the adhesive force of the tape, and finally achieving the detachment of the entire nano-flexible coil device from the silicon substrate to achieve a controllable peeling effect .

Description of drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and together with the description serve to explain the principles of the invention.

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those of ordinary skill in the art, It is said that other drawings can also be obtained based on these drawings without exerting creative work.

Figure 1 is a flow chart of a controllable peeling preparation method of high-density flexible micro-nano coils according to the present invention;

Figure 2 is a schematic structural diagram of the rigid silicon substrate according to the present invention;

Figure 3 is a schematic structural diagram after adding polyimide tape on the rigid silicon substrate of the present invention;

Figure 4 is a schematic structural diagram after adding the first layer of MEMS micro-nano coils based on Figure 3;

Figure 5 is a schematic structural diagram after adding an intermediate insulation layer on the basis of Figure 4;

Figure 6 is a schematic structural diagram after adding a second layer of MEMS micro-nano coils based on Figure 5;

Figure 7 is a schematic structural diagram after adding a stress insulation layer on the basis of Figure 6;

Figure 8 is a schematic diagram of peeling off the entire multi-layer MEMS micro-nano coil from the rigid silicon substrate;

Figure 9 is a schematic diagram of the product after final peeling by the method of the present invention;

Figure 10 is an open circuit voltage output diagram of controllably peeled flexible micro-nano coils of different sizes in a specific embodiment of the present invention.

In the picture: 1. Rigid silicon substrate; 2. Polyimide tape; 3. The first layer of MEMS micro-nano coils; 4. The middle insulation layer; 5. The second layer of MEMS micro-nano coils; 6. Stress insulation layer.

Detailed ways

In order to understand the above objects, features and advantages of the present invention more clearly, the solution of the present invention will be further described below. It should be noted that, as long as there is no conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

In the description, it should be noted that the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. It should be noted that, unless otherwise clearly stated and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; It can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be an internal connection between two components. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

Many specific details are set forth in the following description to fully understand the present invention, but the present invention can also be implemented in other ways different from those described here; obviously, the embodiments in the description are only part of the embodiments of the present invention, and Not all examples.

Specific embodiments of the present invention will be described in detail below with reference to FIGS. 1 to 10 .

In one embodiment, as shown in Figure 1, a controllable peeling preparation method of high-density flexible micro-nano coils includes the following steps:

Step 1: Prepare the rigid silicon substrate 1 and use deionized water and nitrogen to clean the rigid silicon substrate 1. In a specific embodiment, the rigid silicon substrate 1 has a circular sheet structure;

Step 2: At room temperature (20°C) in the process room, paste polyimide tape 2 on the upper surface of the rigid silicon substrate 1 in step 1. The rigid silicon substrate 1 after pasting the polyimide tape 2 is used to make the flexible micro As the base of the nanocoil, the rigid silicon substrate 1 provides a flat surface for subsequent processes. The polyimide tape 2 uses polyurethane glue. Place the rigid silicon substrate 1 on the workbench of the laminating machine, and use the heating function of the laminating machine to melt the rigid silicon Heat the substrate 1 to 80°C to remove water vapor to prevent the bottom of the polyimide tape 2 from bubbling when the polyimide tape 2 is subsequently pasted, affecting subsequent process operations. At the same time, open the vacuum valve of the laminating machine workbench to perform vacuuming. Adsorption, so that the rigid silicon substrate 1 is adsorbed to the workbench of the laminating machine to prevent the rigid silicon substrate 1 from moving during the process of pasting the polyimide tape 2, thus ensuring that there are no bubbles and the surface is smooth during the process of pasting the polyimide tape 2 , and then stick the polyimide tape 2 to the rigid silicon substrate 1; then use deionized water and nitrogen to clean the surface of the polyimide tape 2;

Step 3: Before making a single-layer MEMS micro-nano coil, first sputter the adhesion layer and the seed layer on the surface of the polyimide tape 2. The thickness ratio of the adhesion layer and the seed layer is 1:5 or 1:10. The entire layer and seed layer serve as a conductive layer to prepare for subsequent electroplating work. The adhesion layer and the conductive layer can be respectively a chromium layer and a copper layer, a chromium layer and a gold layer, or a titanium layer and a copper layer. In specific embodiments, chromium is sputtered The layer thickness is 20nm, and the copper layer thickness is 100nm; a single-layer MEMS micro-nano coil is made on the polyimide tape 2 on top of the rigid silicon substrate 1, and then a photosensitive polyimide film is spin-coated, and the photosensitive polyimide film is Photoetch through holes corresponding to the two electrodes of the MEMS micro-nano coil on the imine film; the sub-steps for making a single-layer MEMS micro-nano coil are:

S1. Place the rigid silicon substrate 1 with the conductive layer on the workbench of the glue leveling machine, spin-coat the photoresist model AZ4620, spread the glue at 1000r/min, and perform pre-baking for 150 seconds on a 100°C drying table with an interval in between. After 50 minutes, homogenize the glue for the second time. At this time, the thickness of the photoresist will reach about 15um. Pre-bake for another 150 seconds on the 100°C drying table. Place it at room temperature and use the EVG610 photolithography machine to set the relevant parameters for the photolithography operation. The overall thickness of the rigid silicon substrate 1 and the attachments on it is 620um, of which the photoresist thickness is 15um. Photolithography exposure patterning is performed. At this time, the developer model AZ400K is used with a 1:3 configuration. The development is often At about 55 seconds, use a plasma remover to remove the residual photoresist. The parameters of the plasma remover are set to O2-300W-2min. Finally, the film is hardened on a high-temperature baking table at 120°C for 15 minutes. The first layer of coil template is prepared;

S2. Use the first-layer coil template produced in step 3 to complete the processing of the first-layer micro-nano coil through the electroplating process. The specific operation is: dip a dust-free rod into the acetone solution and wipe it evenly on the circumferential direction of the rigid silicon substrate 1 for ten minutes. Each electrode interface is connected to a power supply clip at the opposite set of electrode interfaces for electroplating of the first layer coil template. The power supply clamp is a DC power supply clamp or an AC power supply clamp; after a certain period of time, it is switched to the next set of opposite electrode interfaces, so that The thickness of the entire electroplating layer will be ensured to be consistent. According to the plating area and the concentration of the plating solution, the calculated current intensity is set to 0.1A. Each electrode is electroplated for 1 minute and 10 minutes, and the ten electrode interfaces are connected in turn until the first layer is 10um thick. MEMS micro-nano coil 3 is prepared;

Step 4: Repeat step 3 until the total number of layers of MEMS micro-nano coils reaches the design requirements; in the same manner as step 3, perform sputtering, photoresist coating, alignment exposure, development and electroplating; in this embodiment, a double-layer coil is set , that is, the double-layer coil includes a first layer of MEMS micro-nano coils 3 and a second layer of MEMS micro-nano coils 5; a photosensitive polyimide film disposed between the multi-layer coils serves as the intermediate insulating layer 4;

Step 5: Finally, spin-coat the photosensitive polyimide film as the stress insulating layer 6 on the top layer for encapsulation. Adjust the thickness of the stress insulating layer 6 to control its stress, and then process the photosensitive polyimide film at 120°C. To dry the film, use the EVG610 photolithography machine to set the relevant parameters. In this example, the double-layer coil is set to have an overall thickness of 620um, and the photosensitive polyimide film is 15um thick. Photolithography exposure patterning is performed, and then diluted Develop with AZ400K developer for about 100 seconds, photo-etch through holes corresponding to the two electrodes of the MEMS micro-nano coil on the stress insulation layer 6; expose the metal electrodes of the flexible coil, and finally cure the photosensitive polyimide film for subsequent connections. conduct electricity;

Step 6: Soak the entire finished product obtained in Step 5 into the acetone solution. After 48 hours, the acetone will react with the polymer polyurethane glue under the polyimide tape 2, thereby reducing the gap between the high-density coil device and the silicon wafer. Due to the viscosity of the stress insulating layer 6 spin-coated on the topmost layer, the tensile stress drives the device film structure to produce cracks, and propagates along the interface between the polyimide tape 2 and the rigid silicon substrate 1, and in the stress insulating layer 6 A layer of flexible handle (such as tape) is attached to the surface. As long as a small force is applied to the handle layer, cracks will form at the abrupt edge of the polyimide tape 2, thereby successfully integrating the multi-layer MEMS micro-nano coil from the whole. The interface between the polyimide tape 2 and the rigid silicon substrate 1 is peeled off to obtain a flexible micro-nano coil.

In this embodiment, a flexible micro-nano coil film was prepared by the method of the present invention, and the resistance of the film was tested without bending. The resistance value of a square coil with a side length of 1 cm is about 60Ω, and the side length is The resistance value of a 1.5 cm square coil is about 100Ω, and the resistance value of a square coil with a side length of 2 cm is about 200Ω. At the same time, on the excitation table, at a frequency of about 7Hz, electromagnetic induction occurs, and the magnetic flux passing through the coil changes. The coil is placed on the side, 2 mm away from the N52 magnet. The measured open circuit voltage output of the above three different side lengths of the coil is about 40mv, about 80mv, and about 120mv respectively. Therefore, the flexible micro-nano coils controlled by this method have good output performance.

The above descriptions are only specific embodiments of the present invention, enabling those skilled in the art to understand or implement the present invention. Although detailed descriptions have been made with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent substitutions for some or all of the technical features; and These modifications or substitutions do not deviate from the essence of the corresponding technical solutions from the scope of the technical solutions of each embodiment, and they should all be covered by the protection scope of the claims.

Claims (6)

1. A controllable stripping preparation method of a high-density flexible micro-nano coil is characterized by comprising the following steps,

step one, preparing a rigid silicon substrate (1) and cleaning the rigid silicon substrate (1);

step two, polyimide tape is stuck on the upper surface of the rigid silicon substrate (1) in the step one

(2) The polyimide adhesive tape (2) adopts polyurethane adhesive, and then the surface of the polyimide adhesive tape (2) is cleaned;

step three, manufacturing a single-layer MEMS micro-nano coil on a polyimide tape (2) on the top of a rigid silicon substrate (1), then spin-coating a photosensitive polyimide film, and photoetching through holes corresponding to two electrodes of the MEMS micro-nano coil on the photosensitive polyimide film;

step four, repeating the step three until the total layer number of the MEMS micro-nano coil reaches the design requirement;

step five, finally spin coating a photosensitive polyimide film serving as a stress insulating layer (6) on the topmost layer for packaging, and photoetching through holes corresponding to two electrodes of the MEMS micro-nano coil on the stress insulating layer (6);

and step six, soaking the whole finished product obtained in the step five in an acetone solution, and peeling off the whole multi-layer MEMS micro-nano coil from the junction of the polyimide adhesive tape (2) and the rigid silicon substrate (1) after a certain time to obtain the flexible micro-nano coil.

2. The method for preparing the controllable stripping of the high-density flexible micro-nano coil according to claim 1, wherein in the first step and the second step, the cleaning treatment is performed by using deionized water and nitrogen.

3. The controllable stripping preparation method of the high-density flexible micro-nano coil is characterized in that in the second step, a rigid silicon substrate (1) is placed on a workbench of a film sticking machine, the rigid silicon substrate (1) is heated to 80 ℃ by utilizing the heating function of the film sticking machine, water vapor is removed, a vacuum valve of the workbench of the film sticking machine is opened, vacuumizing adsorption is carried out, the rigid silicon substrate (1) is adsorbed on the workbench of the film sticking machine, and then a polyimide adhesive tape (2) is stuck on the rigid silicon substrate (1).

4. The controllable stripping preparation method of the high-density flexible micro-nano coil is characterized in that in the third step, before the single-layer MEMS micro-nano coil is manufactured, an adhesion layer and a seed layer are sputtered on the surface of a polyimide adhesive tape (2), the thickness ratio of the adhesion layer to the seed layer is 1:5 or 1:10, and the whole adhesion layer and the seed layer are used as conducting layers.

5. The method for preparing the controllable stripping of the high-density flexible micro-nano coil according to claim 3, wherein in the third step, the sub-steps for preparing the single-layer MEMS micro-nano coil are as follows:

s1, placing a rigid silicon substrate (1) provided with a conductive layer on a workbench of a photoresist homogenizing machine, spin-coating photoresist, performing photoetching exposure patterning treatment by using a photoresist machine after the photoresist reaches a set thickness, performing treatment by using a developing solution, removing residual photoresist by using a plasma photoresist remover, and finally performing hardening treatment on a high-temperature baking table to complete preparation of a first layer of coil template;

s2, dipping an acetone solution, uniformly wiping ten electrode interfaces on the circumferential direction of the rigid silicon substrate (1), connecting a power supply clamp at the position of one group of opposite electrode interfaces to carry out electroplating treatment on the first layer of coil template, switching to the next group of opposite electrode interfaces after a certain time, and connecting the ten electrode interfaces in turn until the whole single-layer coil is prepared.

6. The method for preparing the controllable stripping of the high-density flexible micro-nano coil according to claim 5, wherein the power clamp is a direct-current power clamp or an alternating-current power clamp.