Thin film confinement effects on the thermal properties of model photoresist polymers

Abstract

The demand to print increasingly smaller microelectronic device features means that the thickness of the polymer films used in the lithographic processes must decrease. The thickness of these films is rapidly approaching the unperturbed dimensions of the polymer, length scales at which confinement deviations and dewetting are a significant concern. We combine specular x-ray reflectivity ͑SXR͒ and incoherent neutron scattering ͑INS͒ to probe the thermal stability and dynamical effects of thin film confinement in poly͑hydroxy styrene͒ ͑PHS͒, a polymer used in a majority of the 248 nm deep UV photoresists. PHS forms stable thin films ͑down to 5 nm͒ that do not dewet over a wide temperature range on Si surfaces ranging from hydrophilic to hydrophobic. The surface energy has a profound influence on the magnitude of the thin film expansion coefficient, especially above the glass transition, in films as thick as 100 nm. Confinement also appears to suppress the mean-square atomic displacements and the level of anharmonicity in the dynamics, primarily above the bulk glass transition.

Influence of substrate chemistry and the network homogeneity of ultra‐thin cross‐linked polymer films cured at their surface on the main relaxations temperatures probing by microthermal analysis

“…Any discussion regarding the reasons why the differences in the amine-epoxy segregation are observed surely needs more work to find the complex relationships at sub-micrometre scale between the thickness pertubated by the grafted aminosilane, [20] the resulting amine gradient in the sub-layer, its reactivity and its dependence on the glass transition. In further works we will focus on the quantification of the amine/epoxy ratio in each layer and on precisely measurement of the thickness of the respective layers.…”

Calorimetric glass transition temperature and absolute heat capacity of polystyrene ultrathin films

“…On the practical side, T g dictates, for example, mechanical properties and, for many applications, the maximum use temperature of the material; this is especially important for nanotechnologies that use polymeric thin films, including advanced integrated circuits. 38 On the fundamental side, changes in T g on the nanoscale, and particularly decreases, are not readily explained in the framework of our current understanding of the glass transition. 11 Hence, it is worth emphasizing that not only is the observation of a T g reduction on the nanometer size scale surprising, but its full understanding may lead to a better understanding of the glass transition phenomenon itself.…”

Understanding deviations in lithographic patterns near interfaces: Characterization of bottom anti-reflective coatings (BARC) and the BARC–resist interface

“…So for 50 nm device features, the resist films will be $200 nm thick and the BARC films will be $50 nm thick. This thickness range is typically where the thermal properties of the film (T g and thermal expansion coefficients) start to deviate from the bulk film properties [31][32][33][34][35][36][37][38][39][40][41][42][43]. It is therefore critical to understand the thermal properties of the BARC films and their dependence on film thickness, in order to determine the length scales for the resist-BARC interfacial width and if significant resist-BARC inter-diffusion is possible.…”