Lithography-Related Applications

All books, reviews, and entries on CPs describe the potential applications. Chandrasekhar and others ° have reviewed in comprehensive fashion the applications of CPs, including batteries sensors electro-optic and optical devices microwave- and conductivity-based technologies electrochromic devices electrochemomechanical and chemomechanical devices corrosion protection semiconductor, lithography, and electrically related applications— photovoltaics, heterojunction, and photoelectrochemical cells capacitors electrolytic and electroless metal plating CP-based molecular electronic devices catalysis and delivery of drugs and chemicals membranes and LEDs. 

Besides e-beam lithography, a closely related application of these CP conductive coatings is of course SEM mask metrology and prevention of charging during SEM inspection. Both these fall under the category of conductive coatings for ESD and other applications, discussed in Chapter 19. 

Poly(vinyl cinnamate) is not used in the traditional areas of plastics technology but its ability to cross-link on exposure to light has led to important applications in photography, lithography and related fields as a photoresist. 

Photodimerization of cinnamic acids and its derivatives generally proceeds with high efficiency in the crystal (176), but very inefficiently in fluid phases (177). This low efficiency in the latter phases is apparently due to the rapid deactivation of excited monomers in such phases. However, in systems in which pairs of molecules are constrained so that potentially reactive double bonds are close to one another, the reaction may proceed in reasonable yield even in fluid and disordered states. The major practical application has been for production of photoresists, that is, insoluble photoformed polymers used for image-transfer systems (printed circuits, lithography, etc.) (178). Another application, of more interest here, is the use that has been made of mono- and dicinnamates for asymmetric synthesis (179), in studies of molecular association (180), and in the mapping of the geometry of complex molecules in fluid phases (181). In all of these it is tacitly assumed that there is quasi-topochemical control in other words, that the stereochemistry of the cyclobutane dimer is related to the prereaction geometry of the monomers in the same way as for the solid-state processes. 

Surface tension and contact angle phenomena play a major role in many practical things in life. Whether a liquid will spread on a surface or will break up into small droplets depends on the above properties of interfaces and determines well-known operations such as detergency and coating processes and others that are, perhaps, not so well known, for example, preparation of thin films for resist lithography in microelectronic applications. The challenge for the colloid scientist is to relate the macroscopic effects to the interfacial properties of the materials involved and to learn how to manipulate the latter to achieve the desired effects. Vignette VI provides an example. 

The key operational parameters of exciplex and excimer lasers used in optical lithographic applications include exposure-dose-related parameters comprising average power, pulse energy, repetition rate, and pulse width temporal coherence spatial coherence including beam dimensions, beam divergence, and beam uniformity and maintenance and reliability. Table 13.2 lists some of the key operational parameters of KrF, ArF, and F2 laser systems used in optical lithography. 

Poly(vinyl cinnamate) is conveniently made by the Schotten-Baumann reaction using poly(vinyl alcohol) in sodium or potassium hydroxide solution and cinnamoyl chloride in methyl ethyl ketone. The product is, in effect, a copolymer of vinyl alcohol and vinyl cinnamate, as shown. The polymer has the ability to cross-link on exposure to light, which has led to its important applications in photography, lithography, and related fields as a photoresist (see also Chapter 5). 

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