Polymer dissolution model: an energy adaptation of the critical ionization theory

Abstract

The current scale of features size in the microelectronics industry has reached the point where molecular level interactions affect process fidelity and produce excursions from the continuum world like line edge roughness (LER). Here we present a 3D molecular level model based on the adaptation of the critical ionization (CI) theory using a fundamental interaction energy approach. The model asserts that it is the favorable interaction between the ionized part of the polymer and the developer solution which renders the polymer soluble. Dynamic Monte Carlo methods were used in the current model to study the polymer dissolution phenomenon. The surface ionization was captured by employing an electric double layer at the interface, and polymer motion was simulated using the Metropolis algorithm. The approximated interaction parameters, for different species in the system, were obtained experimentally and used to calibrate the simulated dissolution rate response to polymer molecular weight and developer concentration. The predicted response is in good agreement with experimental dissolution rate data. The simulation results support the premise of the CI theory and provide an insight into the CI model from a new prospective. This model may provide a means to study the contribution of development to LER and other related defects based on molecular level interactions between distinct components in the polymer and the developer.

Patterning of Tailored Polycarbonate Based Non‐Chemically Amplified Resists Using Extreme Ultraviolet Lithography

“…Diffusion of photo-acid is believed to significantly contribute to LER for CAR platforms. [15][16][17] However, it should be noted that other factors such as, mask roughness, [18] aerial image, [19] polymer-developer interactions, [20,21] and secondary electrons, [22][23][24] are also believed to contribute significantly to LER. 22 nm processes are expected to be introduced into manufacturing over the next few years and LER values of less than 1.2 nm are desirable, but are yet to be achieved.…”

Particle generation during photoresist dissolution

“…Mesoscale modeling using this approach not only accounts for the favorable interaction between the ionized part of the polymer and the developer solution to render the polymer soluble as in the Critical Ionization model, but also takes into account the chain configuration and the interactions of the non-ionized part of the chain with the developer and the polymer film. The interaction parameters for different species in the system were based on experimentally determined interfacial energy values and the ionized polymer-developer interaction parameter was determined by calibrating the simulated dissolution rate response to polymer molecular weight and developer concentration against measured values [3,11,12,13]. An aerial image profile produces an acid gradient in the exposed resist film.…”

“…A mesoscale, dynamic Monte Carlo model for photoresist dissolution based on the molecular level interactions between distinct components of the resist and the developer has been developed [3,4]. The stochastic variations in the deprotection profile produced during the post exposure bake (PEB) that are captured by this model are critical for this study.…”

Sensitive polysulfone based chain scissioning resists for 193nm lithography

“…Diffusion of photoacid is believed to be a dominant cause of LER for CAR platforms. [17][18][19] However, a number of other factors are believed to contribute to LER and the major contributors include mask roughness [20] aerial image contrast, [21] polymer-developer interactions [22,23] and energy blur such as diffusion of secondary electrons in the case of EUV lithography. [24,25] Despite the large amount of work investigating issues that affect LER a global understanding of the precise contribution of all the different components is yet to be achieved.…”