Diazoquinone-novolac systems

The polymer resist currently used in chip manufacturing is based on the two-component diazoquinone-novolac system. Novoiac resin is a soft, relatively low-molecular-weight poljnner made from methylphenol and formaldehyde, while the diazoquinone is a bicyclic (two-ring) molecule containing a diazo group (=N=N) adjacent to a ketone carbonyl (C=0). The diazoquinone-novolac mix is relatively insoluble when fresh, but on... 

The diazoquinone-novolac system does not involve photopolymerization or photocrosslinking. It is mentioned, however, to show the importance of photo-chemical reactions in the graptuc arts. 

The diazoquinone-novolac positive plates were only a moderate commercial success, but interest in the diazoqunone-novolac systems was revived in the 1970s when the resolution requirements of the semiconductor industry outpaced the capabilities of the negative bis-azide resists then in use. It was during this time that the diazoquinone resists established themselves as nonswelling, high-resolution imaging materials in the semiconductor industry. 

Chart 2.2. This DQN system employs a cresol-formaldehyde novolac resin as the matrix material. The resin is rendered photosensitive by addition of a diazonaphthoquinone that undergoes photolysis to produce a ketene intermediate that rapidly reacts with water present in the resin to yield an inde-necarboxylic acid. The lipophilic diazoquinone serves to reduce the solubility of novolac films in aqueous base. Photolysis leads to production of an acidic photoproduct that renders exposed areas of the film soluble in aqueous base. 

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). 

Typical vapor phase silylating agents used in top surfaee imaging systems include dimethylsilyldimethylamine (DMSDMA), trimethylsilyldimethylamine (TMSDMA), and trimethylsilyldiethylamine (TMSDEA). Typical liquid phase silylating agents used in top surfaee imaging systems inelude 1,1,33,5,5-hexamethylcyclotrisilazane and bis(dimethylamino)dimethylsilane with N-methyl-2- pyrrolidone (NMP) as a diffusion promoter. Typical polymer resins include polyvinyl phenol and novolac/diazoquinone polymer resins. 

---