Prebake temperature

This indicates that the prebaking temperature higher than the melting point of the azide decomposes the azide (50%) and it totally decomposes upto 100 mJ/cm2 irradiation. It is possible that subsequent reactions of the nitrene, generated from the azide thermolysis and photolysis, with the styrene resin could be responsible for solubility modulation of this type resist (16). 

Figure 33. The interfacial layer thickness as a function of AZ1350J prebake temperature with an AZ dilution of 60% and an 8000-rpm spin speed, resulting in a 0.32-pm film.

Wijdenes and Geomini (170) examined the effects of the phenolic resin composition, its molecular weight distribution, solvent composition, and prebake temperature on the interfacial layer formation. They found that combined use of poly(p-vinylphenol) (structure 3.10) as matrix resin and cyclohexanone as the casting solvent in the diazoquinone resist formulation minimizes mixing of the two layers and yields a capped PCM structure without any plasma treatment. 

The soft bake process can affect the solubility properties of some resists in the developing solvent. For instance, in DNQ/novolac resists, the solubility of the exposed resist as a function of prebake temperatures shows a maximum at around 120°C (Fig. 11.16). Four zones can be distinguished in this plot (i) a no-bake zone where residual solvent and dissolution rates are high, (ii) a low-temperature zone (up to 80°C) where the dissolution rate shows an appreciable decrease due to solvent removal, (iii) a mid-temperature zone (80-110°C) where the DNQ is thermally and preferentially converted to indene carboxylic acid, leading to an increase in dissolution rate, and (iv) a high-temperature zone (>120°C) where the film densification takes place, DNQ is thermally decomposed, the film is depleted of water, and the novolac resin is cross-linked, resulting in dramatic dissolution inhibition. ... 

Figure 7. Resist film thickness as a function of prebake temperature for various blocking levels.

Figure 9. Diffusion coefficient as a function of exposure dose for various prebake temperatures.

Table 1. Resolution capability of resist for various prebake temperatures and t-BOC blocking levels...

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