Overview of the hottest nano image printing techno

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Overview of nano image printing technology


in recent years, the phenomenon of intersection, penetration and integration between different disciplines and technologies is very obvious, and a large number of new disciplines and technologies have emerged. Nanoimprinttechnology, one of the "soft printing technologies", is a new technology that has just emerged. As soon as it appeared on the stage, it was very eye-catching, and followed up one after another to invest in research and development

this technology absorbs the essence of many science and technology, such as nanotechnology, fine processing technology, contact printing technology, interface science and new materials, and was developed after in-depth research. At first glance, this technology is very similar to the hot embossing technology in CD and DVD production. However, after careful comparison, it is not difficult to see that there are obvious differences between the two. The former is only a micron level processing technology, while the latter in many ways shows that it forms images through atomic and molecular level transfer (shift); The former belongs to fine processing in the general sense, while the latter is a processing technology that uses the principles of nano manufacturing to obtain ultra-fine graphics. If we call the former the technology of the 20th century, then the latter is undoubtedly the emerging technology of the 21st century

the reason why nano image printing technology is attractive is that it is different from traditional fine processing (such as photo etching technology, vacuum evaporation technology, electron beam processing technology and chemical etching technology). It does not need harsh processing environment requirements (such as ultra clean workshop, anti shock technical indicators, etc.) and strict condition control (such as constant temperature, constant humidity, high vacuum, etc.), Various nano concave convex patterns can be processed with high precision. It can also produce such products in large quantities and at low cost. In this regard, Miyagi et al. Of Japan made a comparison between soft printing technology including nano image printing technology and traditional technology in their relevant articles

As a highly practical application technology, nano image printing technology will show its unique technical advantages in the production of nano electronic devices, nano optical elements, nano biosensors and other functional graphics with nanostructures

today, people have no doubt that nano image printing technology will have a significant impact on the development of it and microelectronics industry, biology and Life Sciences, environment and new energy technology and other fields (the input power supply must be 3 fires) at the click key speed. The research and development of nano image printing technology began in the mid and late 1990s. It was first initiated by Professor Chou of Princeton University in the United States. After nearly 10 years of research, deepening and technical support, the technology is now entering a preliminary practical stage. At the same time, Professor Chou personally organized and planned a series of relevant international conferences (internationalconferenceonnanoimportnanoprinttechnology simultaneously) to promote the improvement of this technology and expand to the world. The first and second international conferences were held in Boston and other places in the United States in December 2002 and December 2003, respectively. Only one year later, in December 2004, the third international conference was held in Vienna, Austria. Next, the 4th Congress planned will be held in Nara, Japan, in October, 2005. In short, nano image printing technology has taken solid steps from theory to practice, from research and development to preliminary practicality, and its influence has spread all over the world

first, what is nano image printing technology

the so-called nano image printing technology, in the final analysis, is a new type of imprint transfer technology, which will be widely used in the processing and production of high-tech nano concave convex graphics. Its principle is shown in Figure 2. For ease of understanding, the following text is used. Nano image printing technology is to use the mold with nano concave convex image as the "printing plate", use the silicon or glass sheet coated with polymer in advance as the substrate (printed object), and then separate the mold from the substrate after accurate embossing and shaping with the cooperation of corresponding equipment and appliances. At this time, people will find that the nano concave convex image existing on the surface of the mold will be accurately transferred to the polymer film on the surface of the substrate. The transferred image has the same size and depth as the concave convex figure on the mold surface. However, the shape is just the opposite (the image of Yin turning Yang), that is, the convex part of the former is exactly the concave part of the latter, and vice versa. We call this technology, which uses the principle of printing die to transfer nano concave convex graphics, nano image printing technology. As for the technological process of nano image printing, we can summarize and express Professor Chou's early experiments in words as follows

1. Processing and manufacturing of mold mold is an important part of nano image printing, and it is also the "donor" of image. In a sense, the fineness of mold processing will determine the quality of concave convex image transfer. Therefore, the production of mold is particularly important. First, Professor Chou coated a resin (polymethylmethacrylate) film called electronic resist on the template sheet (such as metal, glass, silicon, silicon dioxide/silicon, etc.), and then, according to the pre-designed pattern, directly scanned the mask on the film by electron beam, and then based on this mask, etched the corresponding concave convex image on the template surface by dry etching method. In this way, The mold we need will be made. The experiment shows that the concave convex image with the accuracy of less than 10nm can be transferred with this mold. Professor Chou believes that from the perspective of the transfer technology itself, there is no limit to its clarity, but the quality of the transfer image is largely determined by the processing accuracy of the mold

2. The coated substrate is the "receptor" of image in nano image printing. It consists of two parts: one is the substrate (silicon, silicon dioxide/silicon, glass and other sheets); The second is polymer film. The early polymers used were thermoplastic resins, such as polymethylmethacrylate, polystyrene, polycarbonate, etc. During film formation, people use centrifugation or other coating methods to evenly coat the resin solution on the surface of the substrate to become the substrate for image transfer. 3. Image transfer as described above, the image transfer is imprinted on the film of the substrate through a mold, and then the two are separated after finalization. At this time, the image is transferred. It should be noted here that each thermoplastic resin has its own glass transition temperature (TG). At this temperature, the resin becomes soft and plastic when printed on July 2005 with 7 wires of new technology. On the contrary, below this temperature, the resin becomes a brittle solid. Therefore, before imprinting, we must raise the temperature of the mold and substrate to above the glass transition temperature of the polymer before we can implement the image imprinting project. On the contrary, when the mold is separated from the substrate, in order to ensure that the transferred image does not deform, it is also an essential condition to reduce the temperature to below the glass transition temperature of the polymer before separation. The glass transition temperatures of several commonly used resins are listed in Table 1. Moreover, if the mold we use is quartz glass with very good transparency, and the polymer coated on the surface of the substrate is photosensitive resin, the imprinting and separation of the two do not need to be heated or cooled. Only the imprinted film needs to be exposed to ultraviolet light, and then the photosensitive film is immediately solidified and shaped. Take out the mold, and a transferred concave convex image will appear in front of us. This method is different from the hot embossing process. It is a new process of normal temperature embossing. In short, no matter which embossing method we use, we can obtain concave convex images with an accuracy of several nanometers to hundreds of nanometers

II. Nano image printing process and its characteristics

nano image printing technology so far, a variety of imprint transfer processes have been developed. Now the methods and characteristics of each process are described as follows

1. Hot embossing nano image printing process is called hot embossing nano image printing process (referred to as hot embossing process for short). Since the polymer coated on the substrate is a thermoplastic resin (such as polymethylmethacrylate, etc.), when we raise the substrate temperature to more than 105 ℃ (Tg of polymethylmethacrylate), the resin becomes soft and plastic. At this time, if the mold is stamped on the resin film of the substrate, the soft and plastic resin can be easily extruded and completely fill all the gaps between the mold and the substrate. When the temperature cools and returns below its glass transition temperature (105 ℃), the extruded resin film is cured. At this time, take out the mold, and the nano concave convex image is transferred to the resin film of the substrate. We call this hot embossing and cold setting image transfer process as hot embossing nano image printing process. When we use this process to produce ultra-fine images, the precise positioning of the mold and substrate is essential. To ensure accurate positioning, people often rely on the power of optical microscope. In addition, special tools are also required to fix the mold and the base plate

in a word, when people use the hot embossing process to transfer images on the resin film of the substrate, they can not only process and make various nano concave convex graphics such as single-layer bumps (columns), develop and expand energy-saving service lines or grids, but also obtain nano concave convex images of multi-layer structures on the same substrate through multiple coating and repeated embossing

speaking of this, we cannot forget the new technology of "roller nano image printing", which is a deformation of the hot embossing process. This technology is to make nano concave convex image on the surface of the roller and use it as a mold. The die can be imprinted on a strip-shaped substrate with any length coated with thermoplastic resin, so that any number of concave convex images can be continuously produced on the substrate. It is said that this technology can realize automatic and efficient printing of nano images. It is especially suitable for the fabrication of multi-layer nanostructure graphics

generally, the production cost of single-layer image is lower than that of multi-layer image, and the product price is also cheaper. It has an attractive application prospect in the production of high-density memory disk and diffraction grating. Multilayer nano images will show more attractive technical advantages in the application of optical scoring devices

Figure 5 shows the nano concave convex image made on the polymethyl methacrylate film by the hot embossing process. If we plating nickel on the surface of the image, we can make a high-density disk. Here we should especially point out that if people use functional polymers (optical function, electrical function, biological function, etc.) to replace ordinary polymers on the substrate, it can be found that the original function of the polymer remains unchanged in the hot press transfer. People can easily manufacture functional devices with various uses by using this feature. Such as organic light-emitting devices, broadband optical waveguide polarizing elements, etc

the hot embossing nano image printing process has the following characteristics:

(1) the process is simple and can process products in large quantities

(2) on a large-area substrate (such as a 300mm diameter silicon wafer), nano particles with uniform parts can be produced

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