Photoresist Latent and Developer Images as Probed by Neutron Reflectivity Methods

Abstract

Photoresist materials enable the fabrication of advanced integrated circuits with ever-decreasing feature sizes. As next-generation light sources are developed, using extreme ultraviolet light of wavelength 13.5 nm, these highly tuned formulations must meet strict image-fidelity criteria to maintain the expected performance gains from decreases in feature size. However, polymer photoresists appear to be reaching resolution limits and advancements in measurements of the in situ formed solid/solid and solid/liquid interface is necessary. This Review focuses on the chemical and physical structure of chemically amplified photoresists at the lithographic feature edge at length scales between 1 nm and 100 nm. Neutron reflectivity measurements provide insight into the nanometer-scale composition profiling of the chemical latent image at an ideal lithographic line-edge that separates optical resolution effects from materials processing effects. Four generations of advanced photoresist formulations were examined over the course of seven years to quantify photoresist/photoacid and photoresist/developer interactions on the fidelity of lithographic features. The outcome of these measurements complement traditional resist design criteria by providing the effects of the impacts of the photoresist and processing on the feature fidelity. These physical relations are also described in the context of novel resist architectures under consideration for next-generation photolithography with extreme-ultraviolet radiation.

Using Directed Self Assembly of Block Copolymer Nanostructures to Modulate Nanoscale Surface Roughness: Towards a Novel Lithographic Process

“…The roughness inherent in the photolithographic processes is a major impediment to effective patterning below 32 nm. A method for preparation of surfaces that replicate the side walls of lithographically prepared features has been reported by Prabhu et al72 The method involves preparation of a polymeric film consisting of two layers, where the top layer consists of a PtBMA 0.44 ‐ stat ‐MMA 0.56 resist polymer that contains tertiary ester pendant groups and a PAG, while the bottom layer is an open‐source extreme ultraviolet (EUV) resist polymer, which is based on polyhydroxystyrene chemistry (see Supporting Information, Figure S8),73 and does not contain PAG. When exposed to UV light the PAG molecules in the upper layer undergo photodecomposition to yield a strong acid.…”

“…Preparation of a PHOST‐Based Model Surface that is Similar to Roughness Side Wall Features : The method used is an adaption from the work of Prabhu et al72 An open source EUV resist polymer, poly((4‐hydroxystyrene) 0.6 ‐ stat ‐polystyrene 0.2 ‐ stat ‐PtBMA 0.2 ) (see Supporting Information, Figure S8) (10.0 wt%) was dissolved in PGMEA and trioctylamine (0.07 wt% with respect to the polymer), was also incorporated as the quencher. Note that this solution does not contain PAG.…”

Healing LER using directed self assembly: treatment of EUVL resists with aqueous solutions of block copolymers

“…The test vehicle that was selected to do this in the first instance was a planar rough surface which was prepared using methodology established by Prabhu and coworkers. [50] Briefly, this involved generating a two layer film on a silicon wafer, where the bottom layer was comprised of a poly(hydroxystyrene) based resist polymer that does not contain a photoacid generator. The top layer, or photoacid feeder layer, was comprised of a resist polymer that contained PAG.…”

Deprotection reaction kinetics in chemically amplified photoresists determined by sub-millisecond post exposure bake

“…To test this hypothesis, FT-IR spectroscopy was performed on hot plate and laser heated samples to compare the deprotection byproducts. For the 193 nm resist, the deprotection mechanism is thought to be the cleavage of the adamantyl groups from the C-O ester 12 , resulting in an increased concentration of carboxylic acids (~1700 cm -1 ), and a decreased concentration of C-O ester (~1150 cm -1 ) and adamantyl esters (~1740 cm -1 ). Fig.…”