Polymer films provide a versatile platform in which complex functional relief patterns can be thermally imprinted with a resolution down to few nanometers. However, a practical limitation of this method is the tendency for the imprinted patterns to relax (“slump”), leading to loss of pattern fidelity over time. While increasing temperature above glass transition temperature (Tg) accelerates the slumping kinetics of neat films, we find that the addition of polymer-grafted nanoparticles (PGNP) can greatly enhance the thermal stability of these patterns. Specifically, increasing the concentration of poly(methyl methacrylate) (PMMA) grafted titanium dioxide (TiO2) nanoparticles in the composite films slows down film relaxation dynamics, leading to enhanced pattern stability for the temperature range that we investigated. Interestingly, slumping relaxation time is found to obey an entropy–enthalpy compensation (EEC) relationship with varying PGNP concentration, similar to recently observed relaxation of strain-induced wrinkling in glassy polymer films having variable film thickness. The compensation temperature, Tcomp was found to be in the vicintity of the bulk Tg of PMMA. Our results suggest a common origin of EEC relaxation in patterned polymer thin films and nanocomposites.

Previous studies have shown that the degree of ordering and alignment in block copolymer (BCP) films can be enhanced by increasing the thermodynamic driving force for microphase separation, χN, where χ is the Flory–Huggins interaction parameter between the polymer components and N is the number of statistical segments in the BCP. In practice, this strategy for controlling the microstructure of any BCP film normally involves reducing the temperature T and/or increasing N. However, both of these methods have the drawback of leading to a corresponding slowing down of the rate of ordering and dynamic-heterogeneity-associated defect formation in the material, related to both glass formation and entanglement. In the present work, we explore the use of an ionic liquid (IL) having a high cohesive interaction strength with a relatively low volatility to increase the cohesive interaction parameter χ, while at the same time keeping the molecular mobility high. In particular, we show that IL-driven enhancement of χ and higher molecular mobility, coupled with the poly­(methyl methacrylate) (PMMA) surface wetting interaction strength, induces enhanced substrate-driven stratification of parallel lamellae in polystyrene-b-poly­(methyl methacrylate) BCP (PS–PMMA) films over much larger distances than without IL. We anticipate that this method can be used to prepare relatively defect-free multilayer films wherein the IL is mostly removed under vacuum annealing during the short processing time while preserving the intrinsic lamellar morphology despite the initial high-IL mass fraction. This approach should be extremely useful in applications like barrier materials and batteries, solid-state dielectric capacitors, optical waveguides, and other applications where substrate-parallel multilayer films of controlled thickness are required.

We combine in situ heated atomic force microscopy (AFM) with automated line-by-line spectral analysis to quantify the relaxation or decay phenomenon of nanopatterned composite polymer films above the glass-transition temperature of the composite material. This approach enables assessment of pattern fidelity with a temporal resolution of ≈1 s, providing the necessary data density to confidently capture the short-time relaxation processes inaccessible to conventional ex situ measurements. Specifically, we studied the thermal decay of nanopatterned poly­(methyl methacrylate) (PMMA) and PMMA nanocomposite films containing unmodified and PMMA-grafted silica nanoparticles (SiO2 NP) of varying concentrations and film thicknesses using this new approach. Features imprinted on neat PMMA films were seen to relax at least an order of magnitude faster than the NP-filled films at decay temperatures above the glass transition of the PMMA matrix. It was also seen that patterned films with the lowest residual thickness (34 nm) filled with unmodified SiO2 NP decayed the slowest. The effect of nanoparticle additive was almost negligible in reinforcing the patterned features for films with the highest residual thickness (257 nm). Our in situ pattern decay measurement and the subsequent line-by-line spectral analysis enabled the investigation of various parameters affecting the pattern decay such as the underlying residual thickness, type of additive system, and temperature in a timely and efficient manner.

High aspect ratio (HAR) ONON channel hole patterning in 3D NAND flash presents grand challenges. This report summarizes some of the recent progresses in patterning from a HAR etch and Deposition-Etch-Co-Optimization (DECO) perspective. HAR etch mechanisms will be discussed focusing on how to reduce aspect ratio dependent etching (ARDE) effect. Highlights of the new low temperature etch process will be presented where significant improvement on ARDE is observed. New simulation results from a Monte Carlo feature scale model provide insights in ion scattering and mask interactions on channel hole profile control. Deposition and etch co-optimization (DECO) is a new frontier to enable better channel hole shape control at HAR. Film tier optimization and carbon liner insertion results show improvement in channel hole profile control.

Surface-textured polymer nanocomposite (PNC) films are utilized in many device applications, and therefore understanding the relaxation behavior of such films is important. By extending an in situ wrinkle relaxation method, we observed that the thermal stability of wrinkled PNC films, both above and below the glass transition temperature (T g ), is proportional to a film's nanoparticle (polymer grafted and bare) concentration, with a slope that changes sign at a compensation temperature (T comp ) that is determined to be in the vicinity of the film's T g . This provides unambiguous confirmation of entropy−enthalpy compensation (EEC) as a general feature of PNC films, implying that the stability of PNC films changes from being enhanced to becoming diminished by simply passing through this characteristic temperature, a phenomenon having evident practical ramifications. We suggest EEC will also arise in films where residual stresses are associated with the film fabrication process, which is relevant to nanotech device applications.