Polyimide semiconductor application

In order to develop polyimide films for semiconductor applications, many chemical, mechanical, thermal and film forming characteristics must be determined in order for the user to develop a viable process for reliable integrated circuits. 

Figure 6.6 shows a scheme of the CIELab system. Park and Chang [20] prepared some polyimide nanocomposites films with pristine clay and analyzed the transparency and color change. This is an important aspect since colorless polyimide films have in particular been widely used in electro-optical devices and semiconductor applications. The measurements were obtained for 80 pm thick films by a spectrophotometer and the color coordinates on CIELab system were determined. 

Du Pont produces this polymer under the trade names of Kapton, Pyrafin, Vespel, and Pyre-ML. The trade names refer to polyimides used for film, semiconductor coatings, mol ding applications, and wire enamel, respectively. They have exceUent thermal, electrical, and physical properties. 

Because of the high functional values that polyimides can provide, a small-scale custom synthesis by users or toll producers is often economically viable despite high cost, especially for aerospace and microelectronic applications. For the majority of industrial applications, the yellow color generally associated with polyimides is quite acceptable. However, transparency or low absorbance is an essential requirement in some applications such as multilayer thermal insulation blankets for satellites and protective coatings for solar cells and other space components (93). For interlayer dielectric applications in semiconductor devices, polyimides having low and controlled thermal expansion coefficients are required to match those of substrate materials such as metals, ceramics, and semiconductors used in those devices (94). 

Polvimide-Metal Interfaces. Several technological applications including semiconductor packaging and metallization demand a reliable and durable adhesion properties of the metal films. In the development of multilayer devices consist of alternating layers of metal and polyimides several reliable techniques are needed to study both thin films and their interfaces. The usefulness of the nuclear scattering techniques to study the metallization and the associated interfacial elemental diffusion processes under the effects of various temperature and humidity treatments on the metal-polyimide systems, such as Al, Cu, N, and Au on Du Pont Kapton type H have already been reported (21., 22.). Only a couple of examples are presented here to illustrate the ERD application. 

Just as polymers may be used to form printable semiconductors, so they may be used to form dielectrics as well. Indeed, polymer dielectrics are in widespread use in conventional microelectronics as well. For printed electronics applications, polymer dielectrics are therefore a natural choice for use in printed transistors. Several families of polymer dielectrics have been studied and used in printed transistors. These include various polyimides and other polymer dielectrics such as pol)rvinylphenol (PVP). In general, these dielectrics are characterized by the following properties ... 

Polyimides have many applications in microelectronic industries. They are often used in the electronics industry for flexible cables, as friction elements in data processing equipment, and as insulating films on magnet wires. For example, in a laptop computer, the cable that connects the main logic board to the display (which must flex every time the laptop is opened or closed) is often a polyimide base with copper conductors. Polyimides are used as high-temperature adhesives in semiconductor industries and aerospace industries. They are used for the struts and chassis in cars as well as some... 

An example of a relatively new application for conductive polymers, which has evolved with the semiconductor industry, is in the so-called die-attach adhesives. These typically epoxide- or polyimide-based materials are used to attach silicon integrated circuits to their substrates and leadframe components, and are often required to be electrically conducting so that the back of the chip is effectively earthed. 

Figure 30 Main applications of adhesives in electronic and semiconductor industries (a) polyimide interlayer dielectric films in the fabrication of integrated circuits (b) die attachment in plastic packages (c) die attachment in ceramic packages (d) multichip module with flip chip and surface-mounted devices (e) flexible circuitry (f) tape automated bonding (g) liquid crystal display panels.

Japan Synthetic Rubber Corporation (JSR) was established for the domestic production of synthetic rubber in 1957, but entered the diversified businesses that utilize rubber raw materials fi-om around 1969. The first step was the development of a photosensitive material for semiconductors, and in search of new business, the LCD applications began to surface. Then the discussion started if it could be that new materials need to be synthesized for digital clocks, for example. LCDs at the time were TN-type monochrome displays, in which the alignment layer had to be heated to a high baking temperature of over 300 °C in order to transform the wholly aromatic polyamic acid precursor into polyimide. 

Aromatic polyimides have found wide application in the microelectronics industry as alpha particle protection, passivation, and intermetallic dielectric layers, owing to their excellent thermal stability, mechanical properties and dielectric properties (7-5). Many microelectronic devices, such as VLSI semiconductor chips and advanced multi-chip modules (5), are composed of multilayer structures. In multilayered structures, one of the serious concerns related to reliability is residual stress caused by thermal and loading histories generated through processing and use, since polyimides have different properties (i.e., mechanical properties, thermal expansion coefficient, and phase transition temperature) from the metal conductors and substrates (ceramic, silicon, and plastic) com-... 

Current inventions show improvements in solvent utilization, as follows. PVC-based adhesive for PVC pipes, typically containing solution of PVC in tetrahydrofuran, was replaced by solution of chlorinated PVC in 1,3-dioxolane and/or its derivatives whieh are far less toxic than THF. Ethanol is used in polyimide adhesive and dental adhesive. Monomer solvent mixture is used in crosslinkable acrylate adhesive, which permits formulation of VOC-free composition. Polyurethane hot-melt adhesive produced from polyacrylates and polyesters does not need solvents for its production and cure which occurs under the effect of moisture. Similar observations can be made for sealants. For example, sealing agent for semiconductor light emitting elements have been made from acrylic monomers without application of solvent. Material for production of printed wiring board was produced and cured without solvent from polymethacrylate. It is clear from these examples that new processes are consciously directed towards less toxic solutions. 

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