Diazoketone-resin system

THE DIAZOKETONE/RESIN SYSTEM VACUUM ELECTRON BEAM EXPOSURE... 

While "conventional positive photoresists" are sensitive, high-resolution materials, they are essentially opaque to radiation below 300 nm. This has led researchers to examine alternate chemistry for deep-UV applications. Examples of deep-UV sensitive dissolution inhibitors include aliphatic diazoketones (61-64) and nitrobenzyl esters (65). Certain onium salts have also recently been shown to be effective inhibitors for phenolic resins (66). A novel e-beam sensitive dissolution inhibition resist was designed by Bowden, et al a (67) based on the use of a novolac resin with a poly(olefin sulfone) dissolution inhibitor. The aqueous, base-soluble novolac is rendered less soluble via addition of -10 wt % poly(2-methyl pentene-1 sulfone)(PMPS). Irradiation causes main chain scission of PMPS followed by depolymerization to volatile monomers (68). The dissolution inhibitor is thus effectively "vaporized", restoring solubility in aqueous base to the irradiated portions of the resist. Alternate resist systems based on this chemistry have also been reported (69,70). 

At the present time, most of the positive photoresists used in the manufacture of microcircuits consist of a low molecular weight phenolic resin and a photoactive dissolution inhibitor. This composite system is not readily soluble in aqueous base but becomes so upon irradiation with ultraviolet light. When this resist is exposed, the dissolution inhibitor, a diazoketone, undergoes a Wolff rearrangement followed by reaction with ambient water to produce a substituted indene carboxylic acid. This photoinduced transformation of the photoactive compound from a hydrophobic molecule to a hydrophillic carboxylic acid allows the resin to be rapidly dissolved by the developer. (L2,3)... 

A total synthesis of ( )-royleanone from 5,7,8-trimethoxy-l-tetralone (123) has been described.129 The tetralone was converted into the tricyclic ketone (124), which was in turn converted into 11,12,14-trimethoxypodocarpatriene (125). Demethyla-tion and oxidation afforded the quinone (126 R = H) which was alkylated to give royleanone (126 R = Pr ). Synthetic studies in the resin acid series have led130 to the preparation of the dicarboxylic acid (127) with a cis a/b ring junction. The preparation of some tetracyclic ketones as intermediates for gibberellin synthesis has been described.131 132 The key reaction involves photolysis of a diazoketone (128) to afford the tetracyclic system (129). In a synthesis of phyllocladene from abietic acid... 

The synthesis and characterization of a novel class of diazoketones that function in a manner analogous to the diazoquinones but have bleachable absorbance maxima in the DUV region have been described (Figure 2.9). These systems are reported to function with photosensitivity comparable to that of the DQN systems, but their utihty still appears to be limited by the feet that they are employed in conjuction with a novolac resin, which has a substantial, unbleachable absorbance in the DUV region. This undesirable resin absorbance leads to reduced contrast 24, 25). 

The system chosen to study consisted of the diazoketone J in the resin 2. The diazoketone plays the role of a guest mixed into the host resin. Films were prepared by spin coating onto a silicon substrate using diglyme as a solvent. 

---