Electronics industry photoresists

The majority of 2-methylphenol is used in the production of novolak phenoHc resins. High purity novolaks based on 2-methylphenol are used in photoresist appHcations (37). Novolaks based on 2-methylphenol are also epoxidized with epichlorohydrin, yielding epoxy resins after dehydrohalogenation, which are used as encapsulating resins in the electronics industry. Other uses of 2-methylphenol include its conversion to a dinitro compound, 4,6-dinitro-2-methylphenol [534-52-1] (DNOC), which is used as a herbicide (38). DNOC is also used to a limited extent as a polymerization inhibitor in the production of styrene, but this use is expected to decline because of concerns about the toxicity of the dinitro derivative. 

Many applications of novolacs are found in the electronics industry. Examples include microchip module packaging, circuit board adhesives, and photoresists for microchip etching. These applications are very sensitive to trace metal contamination. Therefore the applicable novolacs have stringent metal-content specifications, often in the low ppb range. Low level restrictions may also be applied to free phenol, acid, moisture, and other monomers. There is often a strong interaction between the monomers and catalysts chosen and attainment of low metals levels. These requirements, in combination with the high temperature requirements mentioned above, often dictate special materials be used for reactor vessel construction. Whereas many resoles can be processed in mild steel reactors, novolacs require special alloys (e.g. Inconel ), titanium, or glass for contact surfaces. These materials are very expensive and most have associated maintenance problems as well. 

The main application of amorphous perfluoropolymers is as cladding of optical fibers, antireflective coatings, low dielectric coatings, and in the electronic industry (e.g., photoresists)1012 and as a low-dielectric-constant insulator for high-performance interconnects.13... 

Organic materials are used in the existing electronics industries mainly for passive purposes insulating and structural support materials. There are, however, exceptions, such as photoresists, liquid crystal displays, and electrocopying. More challenging to many researchers in a diversity of fields is the application of organic conductors from the viewpoint of the fabrication of molecular electronics, to which this chapter is devoted. 

The other change in resist processing involves the use of multilayer schemes in place of a simple photoresist coating. Microimaging using multilayer materials and technology has revolutionized the electronics industry. Many silicon chips used in calculators and computers are produced in some variation of the following sequence of operations ... 

The most used organic component in the electronics industry has been around for several decades already the humble polymer photoresist [7]. This is the shy, retiring partner that is essential for the success of every integrated device in every circuit board. As device feature size has gradually decreased since the invention of the first transistor, refinements in photoresist technology have had to keep pace [8-9]. However, the real excitement will begin in the next decade or two when polymer transistors become commonplace, and when these transistors eventually comprise only a few tens of molecules In a world in... 

Such attractive interactions can be particularly important in situations where the presence of even a few extraneous particles on a surface can be highly detrimental, as in the production of microchips for the electronics industry (Fig. 13.3). The presence of a single dust particle on the surface of a silicon wafer before coating with the photoresist resin that will be used to engrave the final circuit will, in aU probability, result in a defective product in that area. When one considers that modern chips may have circuit line spacings of less than 10 cm, a particle of that diameter or even smaller will represent a veritable monkey wrench in the works. For that reason, extreme measures must be taken to ensure that aerosol particles are absent (to the extent technologically possible) in production areas. 

These chemicals harden between metal parts in the absence of air. They are resistant to shock and vibration, and are used for making locking threads of screws and as sealants, structural adhesives, and as photoresists in photolithography. They are a fairly common cause of sensitisation in the electronics industry. Polyethylene glycol dimethacrylate is the most frequently reported sensitiser [59-62]. The acrylate sealants may also contain stabilisers, accelerators, and other additives which can also cause ACD [62]. 

We conclude this chapter with a discussion of the photoresist, one other type of organic material that is crucial to the electronics revolution. Photoresist technology represents a beautiful amalgam of the polymer chemistry discussed in Chapter 13 and the photochemistry discussed in Chapter 16, all in service of the electronics industry alluded to throughout this chapter. We begin with a basic overview of the process, and then discuss separately the kinds of chemistries involved in negative and positive photoresists. 

The main applications of methyl chloroform in the electronics industry are in circuit board fabrication, where it is used to develop dry film photoresist, and in the semiconductor industry where it is used for secondary cleaning. 

Figure 8.11. The importance of maintaining a clean, aerosol-free atmosphere is vitally important in the electronics industry (a) dust-confaminated semiconductor surface (b) photoresist coated over adhering dust particles (c) developed microcircuit with defects.

This Report follows the format of the previous one except that, commencing this year, the patents section will be omitted. Academic and industrial research in this field continues to be prolific, particularly in areas of photopolymerization such as electron beam curing and photoresists. Other areas, such as the photosensitized degradation of polymers for producing photodegradable plastics, have diminished to only a few articles, and consequently these will now be included in the section dealing with photo-oxidation and photodegradation. 

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