Negative-type photosensitive poly(phenylene ether) based on poly(2,6-dimethyl-1,4-phenylene ether), a crosslinker, and a photoacid generator

A negative-type photosensitive poly(phenylene ether) (PSPPE) based on poly(2,6-dimethyl-1,4-phenylene ether) (PPE), a novel crosslinker 4,4'-methylene-bis [2,6-bis(methoxymethyl)phenol] (MBMP) having good compatibility with PPE, and diphenylidonium 9,10-dimethoxy anthracene-2-sulfonate (DIAS) as a photoacid generator (PAG) has been developed. This resist consisting of PPE (73 wt %), MBMP (20 wt %) and DIAS (7 wt %) showed a high sensitivity (D₀.₅) of 58 mJ/cm² and a contrast (γ₀.₅) of 9.5 when it was exposed to i-line (365 nm wavelength light), postexposure baked at 145 °C for 10 min, and developed with toluene at 25 °C. A fine negative image featuring 6 μm line-and-space pattern was obtained on the film exposed to 300 mJ/cm² of i-line by a contact-printed mode. The resulting polymer film cured at 300 °C for 1 h under nitrogen had a low dielectric constant (ε = 2.46) comparable to that of PPE and a higher Tg than that of PPE. In addition, the cured PSPPE film was pretty low water absorption (