Environmentally stable chemical amplification

Electron spectroscopy for chemical analysis Environmentally stable chemical amplification photoresist Extreme UV... 

A new type of copolymer resist named ESCAP (environmentally stable chemical amplification photoresist) has recently been reported from IBM [163], which is based on a random copolymer of 4-hydroxystyrene with tert-butyl acrylate (TBA) (Fig. 37), which is converted to a copolymer of the hydroxystyrene with acrylic acid through photochemically-induced acid-catalyzed deprotection. The copolymer can be readily synthesized by direct radical copolymerization of 4-hydroxystyrene with tert-butyl acrylate or alternatively by radical copolymerization of 4-acetoxystyrene with the acrylate followed by selective hydrolysis of the acetate group with ammonium hydroxide. The copolymerization behavior as a function of conversion has been simulated for the both systems based on experimentally determined monomer reactivity ratios (Table 1) [164]. In comparison with the above-mentioned partially protected PHOST systems, this copolymer does not undergo thermal deprotection up to 180 °C. Furthermore, as mentioned earlier, the conversion of the terf-butyl ester to carboxylic acid provides an extremely fast dissolution rate in the exposed regions and a large... 

Ito, G. Breyta, D. Hofer, R. Sooriyakumaran, K. Petrillo, and D. Seeger, Environmentally stable chemical amplification positive resist Principle, chemistry, contamination resistance, and lithographic feasibility, J. Photopolym. Sci. Technol. 7, 433 (1994). 

This system, denoted as Environmentally Stable Chemical Amplification Positive Photoresist, ESCAP, has become the standard 248 nm resist in device manufacture by leading chip makers. It is capable of printing features with a density of 125 nm [29]. 

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