CN110562909A - method and device for preparing flexible micro-nano functional structure with large area and high depth-to-width ratio by vacuum pressure forming - Google Patents

Abstract

The invention discloses a method and a device for preparing a flexible micro-nano functional structure with a large area and a high aspect ratio by vacuum pressure forming, and belongs to the field of micro-nano processing. The device mainly includes an airtight airtight chamber composed of an upper casing 1 and a lower casing 3; 1 and the part surrounded by the orifice plate 2 is the upper chamber 12, the part surrounded by the lower side of the film and the lower shell 3 is the lower chamber 11; the bottom of the lower chamber 11 is the mold layer 5, and the mold 5. The upper surface provides a master plate to be embossed; there is an orifice layer 2 parallel to the film layer 8 in the upper chamber 12; the upper chamber 12 and the lower chamber 11 are communicated with the airflow control device 10, The air flow control device 10 can controllably realize the vacuum degree and pressure difference requirements of the upper and lower chambers. There is a heating device 4 at the bottom of the lower casing. The invention simplifies the vacuum equipment and reduces the required volume of the vacuum environment. Air pressure is used to make the film evenly stressed and improve the quality of the product. Surfactants with better mold release effects can be selected during the process. The difficult problem of preparing high aspect ratio structures is solved.

Description

A flexible micro-nano functional junction with large area and high aspect ratio prepared by vacuum pressure forming method and device

Technical field:

The invention discloses a MEMS process preparation method and device for preparing large area and high aspect ratio by vacuum pressure forming. It belongs to the field of micro-nano processing.

technical background:

There are three main types of traditional nanoimprint technology: thermoplastic nanoimprint technology, UV curing imprint technology and micro-contact nanoimprint technology. Nanoimprinting technology is mostly a discontinuous production process, which is difficult to carry out large-scale and large-area production. In order to overcome these difficulties, roller nanoimprinting emerged. Roller nanoimprinting technology has the characteristics of continuous imprinting, high output, low cost and simple system composition. There are two realization processes: one is to make the mask plate directly on the roller, which can be realized by directly etching on the metal roller or using an elastic mask sleeve on the roller, and the rotation of the roller continuously presses the pattern On the substrate that has been spin-coated with photoresist (the temperature reaches above the glass transition temperature), the rolling of the roller realizes two steps of pressing and demoulding. It is also possible to use a roller to roll and apply pressure on the elastic mask, but the uniformity is difficult to guarantee; another process is to combine the roller imprinting technology with the UV imprinting technology, and the UV-cured nano-imprinting technology photoresist itself It is in a liquid state. UV curing can well control the UV beam to the area where the roller and photoresist are separated. The substrate used can be an elastic substrate or a hard substrate such as Si. However, due to the technical characteristics of the roller nanoimprinting technology, the equipment is placed in a vacuum environment as a whole, gas surfactants cannot be used, and the release effect is limited, so it is difficult to process structures with high aspect ratios.

Purpose of the invention:

Aiming at the processing problems of large-area and high-aspect-ratio structures in traditional nanoimprinting, the present invention proposes a method for preparing flexible micro-nano functional structures, which effectively solves the problems of large-area and high-aspect ratio structures. The purpose of the present invention is to provide a method and device for preparing flexible micro-nano functional structures with large area and high aspect ratio by vacuum pressure forming.

Technical solutions:

A device for preparing large-area, high-aspect-ratio flexible micro-nano functional structures by vacuum pressure molding, which mainly includes an airtight airtight chamber composed of an upper shell 1 and a lower shell 3; the chamber is to be The embossed film 8 is divided into upper and lower parts. The part surrounded by the upper side of the film, the upper shell 1 and the orifice plate 2 is the upper chamber 12, and the part surrounded by the lower side of the film and the lower shell 3 is the lower chamber. Chamber 11; the bottom of the lower chamber 11 is a mold layer 5, and the upper surface of the mold 5 provides a master plate to be embossed; the upper chamber 12 has an orifice layer 2 parallel to the film layer 8; Both the upper chamber 12 and the lower chamber 11 are in communication with the airflow control device 10, and the airflow control device 10 is controllable to realize the vacuum degree and pressure difference requirements of the upper and lower chambers. There is a heating device 4 at the bottom of the lower casing, preferably a heating film.

Optionally, a layer of sponge protective layer 9 is pasted on the lower surface of the orifice layer 2 .

The method for preparing a flexible micro-nano functional structure with a large area and a high aspect ratio by vacuum pressure forming of the present invention comprises the following steps:

Step 1: Simultaneously evacuate the upper and lower chambers through the airflow control device 10. It is required that the air flow rate of the upper chamber 12 is greater than that of the lower chamber 11. Deformation occurs, and contact with the mold 5 in advance causes damage to the film 8. During the vacuuming process, the pressure difference on both sides of the film is not greater than P1 to prevent damage to the film 8 caused by excessive pressure difference; The chamber 11 has a higher air pressure than the upper chamber 12, but should be less than 1 Pa. After the vacuuming process is completed, turn on the power supply of the heating film 4 at the bottom of the lower casing 3 to heat the lower casing 3. The outer surface of the casing is required to reach 90°C, and the uniformity is ±2°C. The heat is transferred through the heat transfer method. Inside the shell.

Preferably, P1=100Pa;

Step 2: inject the heated and gasified surfactant 6 into the lower chamber 11 through the airflow control device 10, and simultaneously pressurize the upper chamber 12 so that the pressure difference on both sides of the film 8 is not greater than P1, and the surface to be gasified When the active agent is full of the lower chamber 11, close the air valve 7 and stop pressurizing the upper chamber 12 simultaneously. Wait for the surfactant to be covered with the upper surface of the mold 5 after standing for a period of time;

Step 3: Evacuate the upper and lower chambers again. During the vacuuming process, control the air flow rate of the upper chamber 12 to be greater than that of the lower chamber 11, and make the pressure difference between the two sides of the film 8 not greater than P1 during the vacuuming process; after the vacuuming process, The air pressure in the upper chamber 12 is 0.1-0.3Pa, and the lower chamber 11 is larger than that, but at the same time ensure that the air pressure is lower than 1Pa.

Step 3: Evacuate the upper and lower chambers again, requiring the air flow rate in the upper chamber 12 to be greater than that in the lower chamber 11, and the pressure in the upper chamber 12 should not be greater than that in the lower chamber 11 during the control process. During the vacuuming process, the pressure difference between the two sides of the film 8 is not greater than P1, so as to prevent the film 8 from being damaged by the excessive pressure difference; after the vacuuming process is completed, the upper and lower chambers reach the processing state, and the upper chamber 12 has an air pressure of 0.1-0.3Pa. The lower chamber 11 has a higher pressure than the upper chamber 12, but should be less than 1Pa.

Step 4: pressurize the upper chamber 12 through the air flow control device 10, so that the gas passes through the orifice layer 2 evenly, and the pressure P2 is evenly distributed on the upper surface of the film 8, and the pressure P2 makes more than 80% of the area of the film 8 under the action of pressure contact with the mold. At this time, the casing and the film 8 have reached the glass transition temperature of the material of the film 8. Under the action of pressure, the film 8 undergoes plastic deformation, and then the heating is stopped. After the temperature of the device drops to room temperature, the pressurization of the upper chamber 12 is stopped. , so that the upper chamber 12 and the lower chamber 11 are restored to an atmospheric pressure.

Preferably, the P2 is set to ten atmospheres;

Step 5: Open the upper casing 1 to obtain the embossed patterned film.

Beneficial effect:

The innovation of this device lies in (protection of rights):

(1) Compared with the traditional nanoimprint technology, which places the whole device in a vacuum environment for preparation, this device simplifies the vacuum equipment, reduces the volume required for the vacuum environment, makes the working environment easier to maintain, and shortens the pre-process time. Preparation time, a vacuum environment can be formed within seconds.

(2) Traditional nanoimprinting adopts the method of mechanical pressure, and the structure of the product will be uneven due to the problem of force. This device adopts the method of air pressure to make the film uniform in force and improve the quality of the product.

(3) Because the device adopts the simplified vacuum device mentioned in (1), gaseous surfactant can be used to treat the mold during the process, and the vacuum environment can be quickly restored after the treatment, so the demoulding effect can be better. A surfactant, such as fluorosilane, is used to treat the mold. The difficult problem of preparing high aspect ratio structures is solved.

The invention draws lessons from the vacuum injection molding commonly used in plastic products, and adopts a special pressure forming method to process the film. In order to ensure the processing quality, strict pretreatment of the chamber is required. First of all, the entire working space should be evacuated. This operation avoids the difficulty in compressing the trace air in the mold, resulting in uneven height of the finished product structure; in addition, the surface active agent should be covered with the entire mold surface, so as to avoid the formation of structures during demoulding. The situation of being unplugged. By changing the size of the device, films of different areas can be processed, and the processing of large-area films can be realized; and the processing is carried out in a vacuum environment, which effectively solves the problem that the air volume in the microstructure of the mold cannot be ignored. The invention realizes the purpose of preparing a flexible micro-nano functional structure with a large area and a high aspect ratio by combining vacuum injection molding and demoulding techniques.

It consists of an upper shell 1, a lower shell 3, an orifice plate 2, a film 8, a sealing strip, an airflow control device 10, a surfactant 10, and the like. After the upper shell 1 is buckled, the film 8 for processing is sandwiched between the upper and lower molds, and the cavity in the upper shell 1 and the lower shell 3 is divided into upper and lower parts by the film 8 . The preparation of flexible micro-nano functional structures is achieved through the asynchronous vacuum of the upper and lower chambers. Vacuumize the upper and lower chambers in turn, then inject surfactant gas into the lower chamber, let stand until the active agent is evenly distributed on the surface of the mold 5, then evacuate the lower chamber 11 again, and then apply pressure to the upper chamber 11. Press and heat the lower casing 3, and after the film 8 is fully shaped, the upper casing 1 is opened, and the film is rolled up slowly and evenly by the rollers. By means of vacuuming, the great influence of the residual air in the mold 5 on the molding of the microstructure is avoided, the quality of the product is improved, and the yield of the product is also improved.

Description of drawings:

Figure 1 is a schematic diagram of the device for preparing a large-area, high-aspect-ratio flexible micro-nano functional structure by vacuum pressure forming in the embodiment

FIG. 2 is a partially enlarged view of FIG. 1 .

Fig. 3 is the orifice schematic diagram in the embodiment;

Fig. 4 is a schematic diagram of the pressure change in the working device in the embodiment.

Specific examples:

Referring to Fig. 1-Fig. 3; The device among the present embodiment mainly is made up of following several parts:

Orifice plate: the material of the orifice plate is aluminum plate, the cross section is square, the outermost contour is 84cm, and the working section is 60cm. In order to make the pressure uniform, the small holes of φ6 are evenly distributed on the working section, so that the air pressure is evenly distributed on the film 8 to ensure the processing the quality of. Below the orifice plate 2 is a square groove, and a protective sponge net 9 needs to be pasted in the groove to prevent the film 8 from being overstretched and excessively contacting the upper round hole to cause damage to the film.

Upper shell: The upper shell is made of aluminum plate, the cross section is square, the outermost contour is 68cm, the side length of the working section is 60cm, and there is a sealing groove with a width of 10mm and a depth of 5mm at the lower end of the part. In order to maintain the airtightness of the device, it is tightly connected with the orifice plate through the surrounding holes. Two ventilation holes are processed on the top of the housing, and the ventilation holes are connected with the air flow control device 10 . The edges and corners of the processing interface need to be chamfered.

Lower shell: The material of the lower shell is aluminum plate, the cross section is square, the outermost contour is 84cm, and the side length of the working interface is 60cm. The thread length is 2cm. Because the upper and lower shells need to be opened and closed frequently during operation, hinges are used to connect with the upper shell. The maximum thickness of the lower shell is 2cm. One side of the shell is processed with six threaded holes with a diameter of φ 10. Process a sealing groove with a width of 10mm and a depth of 5mm at a position 4cm away from the working interface, and bury the rubber sealing strip in the groove. In order to keep the chamber well sealed, five vertical through-holes with a diameter of φ20 are processed on the edge of the lower case 3, and are fastened with the upper case 1 by bolts. There is also a through hole connected to the inside of the chamber on the side of the lower casing 3 and connected to the airflow control device 10 . The edges and corners of the processing interface need to be chamfered.

Airflow control device 10: control the entry and exit and speed of airflow to ensure that the pressure change in the device does not exceed the safe range. The airflow control device 10 in this embodiment includes an air pressure valve 7 communicated with the chamber, and a surfactant 6 with heating control. Storage cavity and other parts;

Protective sponge net: small holes are evenly distributed on the sponge net. In order to make the air flow smoothly, the size and position of the holes are the same as those of the orifice plate 2. The thickness is 2mm. The area is 60cmX60cm.

Heating film: polyimide heating film, which can heat evenly after being powered on, the specification is 24V, 50W. Stick it on the bottom of the lower case 3 to heat the device evenly. The area is 70cmX70cm.

The lower casing 3 and the orifice plate 2 need to be equipped with sealing strips to maintain airtightness. The orifice plate 2 and the upper casing 1 are connected by bolts, and it is required to be fastened well so that the sealing strips fit closely, and anti-loosening measures are taken for the nuts to prevent the nuts from loosening and gas leakage during repeated use.

Fix the metal electroformed microstructure mold 5 at the center of the lower casing 3. In order to ensure the processing quality, pay attention not to leave air bubbles under the mold when pasting, and fix the raised corners firmly. A layer of sponge protective net 9 will be pasted on the bottom of the orifice plate to prevent the film 8 from breaking due to uneven pressure changes on both sides of the film 8 .

Using the device in this example to carry out vacuum pressure forming to prepare a large-area, high-aspect-ratio flexible micro-nano functional structure method, first carry out the following preparatory work:

Adjust the air pressure valve 7 before processing, so that the air pressure in the upper chamber 12 decreases slightly faster than that in the lower chamber 11, and the pressure difference does not exceed 100Pa. The purpose of doing this is to prevent the PET film 8 from contacting the mold before the structural forming step 5. Part of the damage is caused to the film 8, which affects the subsequent molding steps, resulting in incomplete structural molding. At the same time, all components need to be assembled for air tightness testing to avoid problems during processing.

At the same time, the microstructure mold 5 of metal electroforming is fixed at the center of the lower casing 3, the sponge protective layer 9 is fixed below the orifice plate 2, and the PET film 8 for processing is fixed above the lower casing 3 to cover the entire working area. section. The heating film 4 used for heating the device is pasted on the bottom center of the lower casing 3 .

After the upper shell 1 and the lower shell 3 are fastened by bolts, a sealed cavity is formed between the two shells, and the PET film 8 is sandwiched between the upper and lower shells, and the closed cavity is divided into upper and lower parts. The part surrounded by the upper side of the film 8 and the upper case 1 is the upper chamber 12 , and the part surrounded by the lower side of the film 8 and the lower case 3 is the lower chamber 11 .

After the commissioning is completed, the specific processing steps are as follows:

Step 1: Vacuum the upper and lower chambers at the same time, and control the air flow rate of the upper chamber 12 to be slightly greater than that of the lower chamber 11, so that the pressure of the upper chamber 12 is slightly lower than that of the lower chamber 11 during the process, so as to prevent the PET film 8 from contacting the mold 5 pairs in advance The film 8 is damaged, and finally the air pressure in the upper chamber 12 is 0.2Pa, and the air pressure in the lower chamber 11 is 0.7Pa. During the vacuuming process, the pressure difference between the two sides of the film 8 is not greater than 100Pa. , to prevent damage to the film 8 due to excessive pressure difference. After vacuuming, turn on the power supply of the heating film 4 at the bottom of the lower casing 3 to heat the lower casing 3. The outer surface of the casing is heated to 90°C with a uniformity of ±2°C, and the heat is transferred by means of heat transfer. Inside the shell.

Step 2: Heat the liquid surfactant 10 (78560-45-9) to vaporize it, inject the surfactant gas into the lower chamber 11, and pressurize the upper chamber 12 at the same time, so that both sides of the film 8 The pressure difference does not exceed 100Pa. After standing for a period of time, the surfactant is covered with the surface of the mold 5;

Step 3: Vacuum the upper and lower chambers again, paying attention to the pressure difference on both sides of the membrane 8 . It is still necessary to make the pressure difference between the two sides of the film 8 not exceed 100Pa, finally the air pressure in the upper chamber 12 is 0.2Pa, and the air pressure in the lower chamber 11 is 0.7Pa.

Step 4: Use the air flow control device 10 to pressurize the upper chamber 12, distribute the air pressure evenly on the upper surface of the film 8 through the orifice plate 2, and the pressure is ten atmospheres, so that the PET film 8 is plastically deformed, and the heating is stopped after fifteen minutes After the temperature of the device drops to room temperature, the pressurization is stopped, and the upper chamber 12 and the lower chamber 11 are connected to the atmosphere in sequence, and the pressure is restored to an atmospheric pressure.

Step 5: Open the closed chamber, and roll up the PET film with a slowly and evenly rolling roller, so far, the preparation process ends.

The pressure changes in the working device are shown in Figure 4, P_0 is the standard atmospheric pressure, the solid line is the pressure of the upper chamber 12, and the dotted line is the pressure of the lower chamber 11. Point a is the initial state, and the pressure of the upper and lower chambers is a standard atmospheric pressure; at the beginning of the step, the upper and lower chambers are evacuated, and the pressure in the upper chamber 12 is controlled during the process to be no greater than that of the lower chamber 11. After the end of the step, the upper and lower chambers reach Point b of the processing state; step 2 inject the vaporized surfactant into the lower chamber through the air flow control device 10, and pressurize the upper chamber 12 at the same time, and stop the upper chamber 12 after the surfactant is filled with the lower chamber 11. Pressurize, at this time the pressure change of the upper and lower chambers reaches point c; Step 3 evacuates the upper and lower chambers again, during the process, the pressure of the upper chamber 12 is still not greater than that of the lower chamber 11, and reaches the processing state point d after the step; 4. Pressurize the upper chamber 12 through the air flow control device 10, preferably, the pressure is ten standard atmospheres, the pressure change of the upper chamber 12 reaches point e, and the lower chamber 11 is always kept in a vacuum state.

Claims (6)

1. A device for preparing a flexible micro-nano functional structure with large area and high depth-to-width ratio by vacuum pressure forming is characterized by mainly comprising an airtight closed cavity formed by an upper shell 1 and a lower shell 3; the cavity is divided into an upper part and a lower part by a film 8 to be imprinted, the part enclosed by the upper side of the film, the upper shell 1 and the orifice plate 2 is an upper cavity 12, and the part enclosed by the lower side of the film and the lower shell 3 is a lower cavity 11; the bottom of the lower cavity 11 is a mold layer 5, and the upper surface of the mold 5 provides a master plate of a pattern to be imprinted; the upper chamber 12 is internally provided with an orifice plate layer 2 parallel to the thin film layer 8; the upper chamber 12 and the lower chamber 11 are both communicated with the airflow control device 10, and the airflow control device 10 can controllably meet the requirements of vacuum degrees and pressure differences of the upper chamber and the lower chamber; the bottom of the lower shell is provided with a heating device 4.

2. The device for preparing the flexible micro-nano functional structure with large area and high aspect ratio by vacuum pressure forming according to claim 1, wherein the heating device 4 at the bottom of the lower shell is a heating film.

3. The device for preparing the flexible micro-nano functional structure with large area and high aspect ratio by vacuum pressure forming according to claim 1, wherein a sponge protective layer 9 is applied to the lower surface of the pore plate layer 2.

4. a method for preparing a large-area high-aspect-ratio flexible micro-nano functional structure by the device according to any one of claims 1 to 3, comprising the following steps:

The method comprises the following steps: the upper chamber and the lower chamber are simultaneously vacuumized through the airflow control device 10, the air flow rate of the upper chamber 12 is required to be larger than that of the lower chamber 11, and the pressure of the upper chamber 12 is not larger than that of the lower chamber 11 in the control process, so that the film 8 is prevented from deforming under the pressure difference and contacting the die 5 in advance to damage the film 8; in the process of vacuumizing, the pressure difference between two sides of the film is not greater than P1, so that the film 8 is prevented from being damaged due to overlarge pressure difference; after the vacuumizing process is finished, the upper chamber and the lower chamber reach a processing state, the air pressure of the upper chamber 12 is 0.1-0.3Pa, and the air pressure of the lower chamber 11 is greater than that of the upper chamber 12 but less than 1 Pa; after the vacuumizing process is finished, a power supply of a heating film 4 at the bottom of the lower shell 3 is connected, the lower shell 3 is heated, the outer surface of the shell is required to reach 90 ℃, the uniformity is +/-2 ℃, and heat is transferred into the shell in a heat transfer mode;

Step two: injecting the heated and gasified surfactant 6 into the lower chamber 11 through the airflow control device 10, pressurizing the upper chamber 12 at the same time, so that the pressure difference between two sides of the membrane 8 is not more than P1, closing the air pressure valve 7 when the lower chamber 11 is filled with the gasified surfactant, and stopping pressurizing the upper chamber 12 at the same time; standing for a period of time until the surface active agent is fully distributed on the upper surface of the mould 5;

Step three: vacuumizing the upper chamber and the lower chamber again, controlling the air flow rate of the upper chamber 12 to be higher than that of the lower chamber 11 in the vacuumizing process, and ensuring that the pressure difference between two sides of the film 8 is not more than P1 in the vacuumizing process; after the vacuum pumping process is finished, the air pressure of the upper chamber 12 is 0.1-0.3Pa, the ratio of the lower chamber 11 is large, and meanwhile, the air pressure is ensured to be lower than 1 Pa;

Step three: vacuumizing the upper and lower chambers again, wherein the air flow rate of the upper chamber 12 is required to be larger than that of the lower chamber 11, and the pressure of the upper chamber 12 is not larger than that of the lower chamber 11 in the control process; in the process of vacuumizing, the pressure difference between two sides of the film 8 is not greater than P1, so that the film 8 is prevented from being damaged due to overlarge pressure difference; after the vacuumizing process is finished, the upper chamber and the lower chamber reach a processing state, the air pressure of the upper chamber 12 is 0.1-0.3Pa, and the air pressure of the lower chamber 11 is greater than that of the upper chamber 12 but less than 1 Pa;

Step four: pressurizing the upper chamber 12 through the air flow control device 10 to enable air to uniformly pass through the pore plate layer 2, uniformly distributing the pressure P2 on the upper surface of the film 8, and enabling more than 80% of the area of the film 8 to be in contact with the die under the action of the pressure P2; at this time, the shell and the film 8 reach the glass transition temperature of the film 8 material, the film 8 is plastically deformed under the action of pressure, then the heating is stopped, and after the temperature of the device is reduced to the room temperature, the pressurization of the upper chamber 12 is stopped, so that the upper chamber 12 and the lower chamber 11 are restored to the atmospheric pressure;

Step five: and opening the upper shell 1 to obtain the embossed patterned film.

5. The method for preparing a large-area high-aspect-ratio flexible micro-nano functional structure according to claim 4, wherein in the first step, P1 is 100 Pa.

6. The method for preparing a large-area high-aspect-ratio flexible micro-nano functional structure according to claim 4, wherein P2 is set to ten atmospheric pressures in the fifth step.