Ketal resist systems

Name of a positive electron beam resist (ketal resist system)... 

Early version of the ketal resist system (KRS) from IBM partially 2-methoxypropyl (ketal)-protected PHOST, partially 2-benzyloxypropyl (ketal)-protected PHOST. 

It should be pointed out that the solubility change in all chemically amplified resists (CARs) occurs only in the dark reaction during the PEB. Some of the CARs such as acetal and ketal systems have low activation energy, so deprotection can occur with low-temperature PEBs or even at room temperature. In the absence of thermally driven diffusion such as in acetal and ketal resist systems, BARCs must be used for resists with such low PEB temperatures, which are significantly lower than the soft bake temperature, in order to control reflectivity issues associated with standing waves. 

Since the introduction of chemically amplified resist systems to DUV technology, the environmental stability and bake latitudes have been the major concern of this type of chemistry. Ketal resist systems have been very robust towards fiiese issues. The methoxypropene protected polyhydroxystyrene resist is our first initial work on ketal system. 

Other three-component systems based on this chemistry have made use of the following acid-labile dissolution inhibitors polyphthalaldehyde (80), ketals of (J-ketoesters (81), and compounds containing C-O-Si bonds (82). Similar resists have also been used with other radiation sources these will be discussed in subsequent sections. 

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