The development of high-efficiency nonlinear optical (NLO) polymers has opened up many opportunities in the field of electro-optics. However, current NLO polymers do not meet stability requirements for semiconductor integration. In an effort to improve this, we examined the effects of crosslinking following electric field poling. A series of photocrosslinkable polymers bearing side chain chromophores was synthesized, poled and evaluated on the basis of the thermal stability of Second Harmonic Generation. Photoinitiation allowed for control of the onset of curing. Crosslinking was monitored by FTIR and optimal conversion was achieved by applying a slow temperature ramp during exposure. The ultimate stability of the poled polymers was directly related to the number of crosslinking substituents attached to the chromophore pendant group. With two reactive groups per chromophore significant SHG was retained at temperatures beyond the polymer Tg. In integrated circuit packaging there is a need for directly-patternable polymers of low dielectric constant. Bridging the gap between the high-value silicon chip and circuit board is a substrate comprising alternating layers of metal conductor and polymer dielectric. PMDA-ODA, an aromatic polyimide, meets many of the requirements for integration and can be patterned using a photobase generator (PBG). Due to absorbance by the PMDA-ODA precursor, this PBG must have activity at visible wavelengths. Several oxime urethanes were synthesized and evaluated as candidate long wavelength PBG. These compounds exhibit clean photochemistry and high visible light sensitivity. Unfortunately, carbamate thermal stability is insufficient for patterning PMDA-ODA. For improved material properties, PMDA-TFMB, a fluorinated polyimide, was also evaluated. Importantly, the polymer precursor is sufficiently transparent to employ thermally-stable near-UV photobases. With photobase, 2.5 micron features were resolved in PMDA-TFMB. An ancillary benefit of this methodology is reduced cure temperature (~200 °C), a traditional drawback of polyimides. This material demonstrates a dielectric constant near 3 and a thermal expansion coefficient (CTE) of approximately 6 ppm/°C in-plane. Through-plane thermal expansion is somewhat problematic, with a CTE of approximately 160 ppm/°C, and will likely require a nanoparticle composite strategy. However, this combination of material and lithographic properties make PMDA-TFMB a promising candidate for this application. / text

In recent years the microelectronics industry as found itself at an impasse. The tradition pathway towards smaller transistors at lower costs has hit a roadblock with the failure of 157 nm lithography and the continued delays in 13.5 nm extreme ultra violet light sources. While photolithography has been able to keep pace with Moore’s law over the past four decades, alternative patterning technologies are now required to keep up with market demand. The first section of this dissertation discusses the new resolution enhancement technique develop in the Willson lab termed pitchdivision. Through the incorporation of specifically tailored photobase generators (PBGs) into commercially available resists, the resolution of current 193 tools may be doubled. Special two-stage PBGs were designed and synthesized to increase the image fidelity of pitchdivision patterns. The next project deals with the design, synthesis, and evaluation of resists that find amplification through unzipping polymers. An aromatizing polyester polymer that acts as dissolution inhibitor in novolac and is inherently sensitive to 13.5 nm exposure is discussed. Initial results show excellent sensitivity and promise towards a new class of EUV resists. / text

La photopolymérisation est un procédé en plein essor qui permet d’accéder à des matériaux polymères, notamment sous la forme de films ou de revêtements. Néanmoins, celle-ci est majoritairement basée sur un mécanisme de polymérisation radicalaire qui proscrit l’obtention de matériaux totalement biodégradables. Aussi, au cours de cette thèse, nous nous sommes intéressés à la photopolymérisation par ouverture de cycle (photoROP) d’esters et de carbonates cycliques à l’aide de deux grandes familles de photogénérateurs de bases (PBGs). Tout d’abord, des PBGs, pouvant libérer des superbases de type amidine et guanidine cycliques ont été employées pour mener efficacement la photoROP du L-LA et du TMC en solution. Puis, nous nous sommes attachés à développer, sur le modèle des photobases précédentes, de nouveaux PBGs qui libèrent sous irradiation UV des carbènes N-hétérocycliques (NHCs). La libération des NHCs à partir de ces « NHCs photolatents » a été prouvée par RMN 1H et par la formation d’adduits NHC.CS2. De même, ces PBGs se sont révélés actifs pour la photoROP du L-LA et du TMC en solution, mais avec une plus faible efficacité que les PBGs précédents. En effet, les cinétiques de polymérisation sont lentes du fait de la présence de CO2 dans le milieu (libéré lors de l’irradiation UV) qui conduit à la formation d’adduit NHC.CO2 inactif en ROP. Ainsi, la photobase la plus performante, libérant du TBD, a été employée afin d’effectuer la photoROP en masse d’esters cycliques liquides (ε-CL, δ-VL et un mélange innovant L-LA/TMC). Finalement, des réseaux ont été formés par incorporation dans le milieu réactionnel d’un monomère bifonctionnel, permettant d’obtenir sur demande (contrôle temporel) des matériaux réticulés potentiellement entièrement biodégradables. / Photopolymerization is a growing process allowing preparing polymer materials, notably in the form of films or coatings. Nevertheless, it is mostly based on a radical polymerization mechanism that prevents obtaining fully biodegradable materials. The goal of this PhD work was thus to develop the photopolymerization of cyclic esters and carbonates by using two families of photobase generators (PBGs). First, already described PBGs, releasing cyclic amidine and guanidine-type superbases, were effectively employed to carry out the photopolymerization of L-LA and TMC in solution. Then, taking previous PBGs as models, we developed new PBGs able to release N-heterocyclic carbenes (NHCs) under UV irradiation. The release of NHCs from these “photolatent NHCs” was proven both by 1H NMR and by the formation of NHC.CS2 adducts. These PBGs also proved to be active for the ROP of L-LA and TMC in solution, but to a lesser extent than previous photobases. Indeed, slower kinetics of polymerization were observed, which was attributed to the presence of CO2 in the reaction medium (CO2 released by photodegradation of the PBG) that leads to the formation of NHC.CO2 adduct (inactive for ROP). Thus, the most efficient photobase (releasing TBD) was employed to carry out the bulk photopolymerizations of liquid cyclic esters (ε-CL, δ-VL and even an innovative L-LA / TMC mixture). Finally, polymer networks have been formed by incorporating a bifunctional monomer into the reaction medium, allowing the preparation “on demand” (temporal control) of potentially fully biodegradable materials in a one-pot process.

The ubiquity of particulate contamination requires dust mitigation techniques to provide low-scatter surfaces and edges on sensitive optical devices in space. Poly(olefin sulfone)s have been shown to photodegrade with the assistance of a photobase generator when exposed to UV light (254 nm) and heat (120 °C). These polymers may be useful for minimizing dust on optical surfaces for space applications. However, their behavior in vacuum has not been fully characterized. We synthesized poly(2-methyl-1-pentene sulfone) (PMPS) and poly(1-hexene sulfone) (PHS) with and without a photobase generator. We studied the photodegradation (172 nm or 254 nm) of thin films in vacuum. Spectroscopic ellipsometry was used to quantify film thickness over time. The PMPS and PHS films both degraded when exposed to UV light in vacuum, though PHS to a lesser degree. We found that heat was not required to cause degradation, and that degradation occurred with UV irradiation even without a photobase generator. We also found that the degradation process removes dust particles as the film disappears. This investigation shows that poly(olefin sulfone)s could be used to protect optical surfaces until after their deployment in space.

The relentless commercial drive for smaller, faster, and cheaper semi-conductor devices has pushed the existing patterning technologies to their limits. Photolithography, one of the crucial processes that determine the feature size in a microchip, is currently facing this challenge. The immaturity of next generation lithography (NGL) technology, particularly EUV, forces the semiconductor industry to explore new processing technologies that can extend the use of the existing lithographic method (i.e. ArF lithography) to enable production beyond the 32 nm node. Two new resolution enhancement techniques, double exposure lithography (DEL) and pitch division lithography (PDL), were proposed that could extend the resolution capability of the current lithography tools. This thesis describes the material and process development for these two techniques. DEL technique requires two exposure passes in a single lithographic cycle. The first exposure is performed with a mask that has a relaxed pitch, and the mask is then shifted by half pitch and re-used for the second exposure. The resolution of the resulting pattern on the wafer is doubled with respect to the features on the mask. This technique can be enabled with a type of material that functions as optical threshold layer (OTL). The key requirements for materials to be useful for OTL are a photoinduced isothermal phase transition and permeance modulation with reverse capabilities. A number of materials were designed and tested based on long alkyl side chain crystalline polymers that bear azobenzene pendant groups on the main chain. The target copolymers were synthesized and fully characterized. A proof-of-concept for the OTL design was successfully demonstrated with a series of customized analytical techniques. PDL technique doubles the line density of a grating mask with only a single exposure and is fully compatible with current lithography tools. Thus, this technique is capable of extending the resolution limit of the current ArF lithography without increasing the cost-of-ownership. Pitch division with a single exposure is accomplished by a dual-tone photoresist. This thesis presents a novel method to enable a dual-tone behavior by addition of a photobase generator (PBG) into a conventional resist formulation. The PBG was optimized to function as an exposure-dependent base quencher, which mainly neutralizes the acid generated in high dose regions but has only a minor influence in low dose regions. The resulting acid concentration profile is a parabola-like function of exposure dose, and only the medium exposure dose produces a sufficient amount of acid to switch the resist solubility. This acid response is exploited to produce pitch division patterns by creating a set of negative-tone lines in the overexposed regions in addition to the conventional positive-tone lines. A number of PBGs were synthesized and characterized, and their decomposition rate constants were studied using various techniques. Simulations were carried out to assess the feasibility of pitch division lithography. It was concluded that pitch division lithography is advantageous when the process aggressiveness factor k₁ is below 0.27. Finally, lithography evaluations of these dual-tone resists demonstrated a proof-of-concept for pitch division lithography with 45 nm pitch divided line and space patterns for a k₁ of 0.13. / text