Low ceiling temperature, thermodynamically unstable polymers have been troublesome to synthesize and keep stable during storage. In this study, stable poly(phthalaldehyde) has been synthesized with BF 3 -OEt 2 catalyst. The role of BF 3 in the polymerization is described. The interaction of BF 3 with the monomer is described and used to maximize the yield and molecular weight of poly(phthalaldehyde). Various Lewis acids were used to investigate the effect of catalyst acidity on poly(phthalaldehyde) chain growth. In situ nuclear magnetic resonance was used to identify possible interactions formed between BF 3 and phthalaldehyde monomer and polymer. The

Low ceiling temperature polyaldehydes are of interest for transient materials because the temperature of depolymerization can be at or below room temperature. There is interest in expanding the number of aldehydes which can be copolymerized so as to change the vapor pressure and other properties of the depolymerized products. Although fast depolymerization has been achieved with polyaldehydes, the rate of monomer evaporation after depolymerization can be controlled by incorporating lower molecular weight monomers into the polymer. High vapor pressure aliphatic aldehydes have been copolymerized with low vapor pressure and high reactivity phthalaldehyde to create stable, high molecular weight polymers with high vapor pressure. A method for measuring the depolymerization time by quartz crystal microbalance has been developed. The copolymer of phthalaldehyde and butanal improves the evaporation time for the polymer by a factor of 11. The onset of thermal decomposition of the copolymer was increased from 107 C for the phthalaldehyde homopolymer to 141 C for the copolymer. The tensile strength of the copolymer was 0.8-1.6 GPa.

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...

The mechanical properties of an aqueous developed, chemically amplified, polynorbornene-based permanent dielectric have been investigated. The previously reported hexafluoroisopropanol norbornene and tert-butyl ester norbornene copolymer has been modified via two routes to improve the mechanical properties of the polymer and enable thick-film deposition. First, a third monomer, butyl norbornene (ButylNB) was added to the polymer backbone. The inclusion of 24 mol% ButylNB lowered the elastic modulus from 2.64 to 2.35 GPa and raised the dielectric constant from 2.78 to 3.48. The second approach added a low molecular weight, plasticizing additive in the copolymer formulation. Many additives were immiscible with the resin or did not affect the mechanical properties. Trimethyololpropane ethoxylate (TMPEO) was found to be a miscible additive that improved mechanical properties and could participate in crosslinking the final dielectric material. TMPEO interacted with the PAG, lowering its decomposition temperature. An optimal formulation and processing scheme were determined. A formulation with 10 pphr TMPEO was measured to have a dielectric constant of 2.94, an elastic modulus of 1.95 GPa, a sensitivity at 365 nm of 175 mJ/cm 2 , and a contrast of 4. Photo-definable, permanent, low-k dielectrics are widely used in the fabrication of microelectronic devices and packages.1-5 These dielectrics electrically isolate the interconnect and mechanically stabilize the structures for the life of the device. On integrated circuits, organic dielectrics can be used for interlayer isolation and/or the stress buffer layer on top of the device. Stress buffer layers protect the top surface of the chip and can mitigate mechanical failures that arise from a mismatch of the coefficient of thermal expansion between the chip and package during thermal cycling. In microelectronics packages, low-k dielectrics can be used in the buildup layers, electrically separating the electrical conductors. Low permittivity is critical for use in these applications, as it affects device performance, energy loss, and signal integrity.Photo-definability is an attractive property for permanent polymeric dielectrics. The ability to directly pattern the dielectric by photolithographic techniques mitigates the need for a separate photoresist and pattern transfer steps. This can lower the overall fabrication cost and reduce the number of individual process steps.2 For stress buffer and redistribution applications, positive tone photo-definable dielectrics are more desirable than negative tone ones because the lithographic mask is mostly opaque mask and less prone to transfer particle defects. Also, holes and lines in positive tone materials exhibit sloped sidewalls (opening wider at the top) which is beneficial for void-free plating of the copper interconnects. Aqueous developability is another attractive property, as it mitigates the need for environmentally harmful organic solvent developers. Further, the dielectric should exhibit high sensitivity and contrast ...

A highly light sensitive, positive tone, low-k dielectric has been developed with excellent lithographic, mechanical, and electrical properties. The photolithographic solubility switching mechanism is based on well-studied, chemically amplified chemistry. The dielectric is composed of a polynorbornene backbone with pendent fluoroalcohol and tert-butyl ester functional groups. The effects of the photoacid generator and monomer ratio on lithographic, mechanical, and electrical properties are studied. The sensitivity (D100 = 8.09 mJ/cm2) and contrast (γ ≥ 14.2) are an order of magnitude higher than existing positive tone dielectrics. The dielectric can be cross-linked via a Fischer esterification after patterning. For one monomer composition (60% fluoroalcohol), the modulus and hardness were measured to be 2.99 GPa and 0.252 GPa, respectively. The dielectric constant for this composition was found to be 2.78.