Acid‐Catalyzed degradation mechanism of poly(phthalaldehyde): Unzipping reaction of chemical amplification resist

Chemically amplified resists. VII. proton generation from triphenyl sulfonium salts via photochemical isomerization mechanism.

“…From those calculations carried out in this paper, we conclude that the concerted mechanisms are mainly operated in the direct photolysis of triphenylsulfonium salts in the singlet states, whereas the homolytic bond-dissociation mechanism is operated in the triplet state arisen from photo-irradiation as well as in the triplet-sensitized photolysis as shown in the previous paper [4] . This mechanism presented here explains clearly the two serious questions indicated above.…”

Triggered Transience of Metastable Poly(phthalaldehyde) for Transient Electronics

“…These metastable polymers must fulfill several technical criteria: i) displaying suitable performance as a substrate or encapsulant for microelectronic packaging, ii) undergoing environmentally triggered depolymerization that deactivates the electronics, and iii) allowing for tunable degradation kinetics. Among the metastable polymers reported to date, poly(phthalaldehyde) (PPA) is an ideal candidate for this application due to its low ceiling temperature ( T c = −43 °C), easy synthesis with various end‐groups, and its rapid depolymerization upon backbone bond cleavage . PPA has been used as an acid‐degradable photoresist, and its linear, end‐functionalized derivatives synthesized by anionic polymerization have been shown to depolymerize selectively in the presence of chemical triggers …”

Stable, High‐Molecular‐Weight Poly(phthalaldehyde)

“…Poly(phthalaldehyde) (PPHA) is highly sensitive to acid and has been shown to rapidly depolymerize when deprotected either by end‐group removal or direct chain attack . The polymerization of phthalaldehyde (PHA) can proceed by either an anionic or cationic mechanism .…”