A low permittivity, positive tone, polynorbornene dielectric has been developed that exhibits excellent lithographic and electrical properties. The polymer resin is a random copolymer of a norbornene hexafluoroalcohol (NBHFA) and a norbornene tert-butyl ester (NBTBE). High optical sensitivity and contrast were achieved using a chemically amplified solubility switching mechanism through the acid-catalyzed deprotection of the tert-butyl ester functionality. After developing in aqueous base, the film was thermally cured through a Fischer esterification reaction, resulting in a cross-linked permanent dielectric. The effect of the photoacid generator (PAG) concentration on the lithographic patterning and curing reactions was studied. Higher PAG loading was favorable for both sensitivity and dielectric constant. The sensitivity of a formulation was measured as low as 8.09 mJ/cm 2 . The molar ratio of the two monomers composing the polymer was varied. A higher NBHFA content was favorable because it resulted in a lower modulus, lower shrinkage, and lower dielectric constant and loss. A formulation with 70 mol% of the NBHFA had a modulus of 2.60 GPa, a 12.2% volume decrease during cure, and a dielectric constant of 2.23. The direction-dependent coefficient of thermal expansion was measured, and it was found that the anisotropy of the PNB films decreased with higher NBTBE content. Permanent dielectric materials are used in microelectronic devices and packages to separate and insulate components and interconnect. Low dielectric constant (low-k) insulators are desirable for on-chip, chip-to-chip, chip-to-package, and on-package wiring to avoid electrical delay and lower the energy consumed in the signal interconnect. [1][2][3] Polymers are widely used for these purposes because they offer a low-stress, easily processed alternative to inorganic dielectrics. [2][3][4][5] In addition, photosensitive dielectrics are desirable because they can be directly patterned by photolithographic means. Lithographically printed dielectrics do not require the use of photoresist or additional pattern transfer steps, which can be costly and expose the device to aggressive wet or dry etch process steps.Positive tone dielectrics are especially attractive because they result in sloped sidewalls that are generally favored for void-free electroplating of copper. Positive tone materials also exhibit better process yield because exposures through dark-field masks are less susceptible to particle defects. The ability to develop the latent image in an aqueous base developer mitigates the need for environmentally unfriendly organic solvent developers. High sensitivity is very important since it directly leads to higher throughput and tool utilization since less optical energy is required for the solubility switching reaction. The sensitivity of the photopatternable material is coupled to the quantum efficiency of the photoactive compound. Poor quantum efficiency often requires a high loading of the photoactive compounds to effect the inhibition or solu...