Positive-tone chemically amplified photosensitive polyimides with controllable taper angles

Abstract

Current methods for tuning the taper angle of photosensitive polyimide (PSPI) often require additional equipment or materials, and has limited achievable angle tuning range while maintaining resolution. To overcome these limitations, a positive tone chemically amplified photosensitive polyimide (p-CA-PSPI) was prepared from tert-butylcarbonate-protected polyimide (t-Boc-PI), photoacid generator (PAG), other additives, and solvent. By optimizing the protection ratios of t-Boc-PI resins, the p-CA-PSPI achieved a high film retention rate and wide processing window. The photo-patterning conditions were able to manipulate the sidewall profile and taper angle within the range of 11–53°, maintaining a resolution of 3 μm for patterns with taper angles higher than 28° at 1.5 μm film thickness, by controlling the acid diffusion. The thermally cured polyimide films demonstrated excellent mechanical properties, including a tensile strength of 95.7 MPa, tensile modulus of 2.9 GPa, and elongation at breakage of 24.2%, high thermal stability with a glass transition temperature of 343 °C, decomposition temperature of 409 °C, and good chemical resistance. This novel taper angle tuning method has the potential to optimize the internal stress of semiconductor devices and advance the development of display devices, MEMs, and multifunctional electronics that require a single package containing multiple or unique taper profiles.