For the patterning of sub-100 nm features, a clear understanding of the origin and control of line edge roughness (LER) is extremely desirable, from a fundamental as well as a manufacturing perspective. With the migration to thin photoresists coupled with bottom antireflective coating (ARC)-hardmask underlayers, LER analysis of the developed resist structures is perhaps an inaccurate representation of the substrate roughness after the etch process, since those underlayers can play a significant role in increasing/decreasing linewidth variations during the image transfer process and hence can impact the device performance. In this article, atomic force microscopy is used to investigate the contribution of the imaging resist sidewall topography to the sidewall roughness of the final etched feature in thin photoresists, ARC, and hardmasks. Resist systems suitable for 248 and 193 nm lithography as well as fluorine-containing resists were processed using N2-H2 or fluorocarbon plasma etch. It is shown that the interaction of different etch chemistries with existing sidewall profiles can result in loss of the original morphological information and creation of new spatial frequency domains that act as physical templates for subsequent image transfer processes. Excessive roughness transfer into the hardmask layer due to insufficient resist thickness or inadequate etch resistance originates from striation propagation from the resist layer into the hardmask layer. In the case of fluorine-containing materials, a decreased etch resistance and reduced initial film thickness values give rise to critical underlayer roughening during plasma etch. Based on the results shown, it is predicted that advanced resist systems for 157 nm lithography and beyond will require the use of ARC layers with built-in hardmask properties in those particular cases in which patterning of deep trenches is needed, in order to maintain LER values within acceptable levels.
A Monte Carlo simulator was developed to simulate the profile evolution during the Cl etching of patterned polysilicon in high density plasma etchers. The simulator used Monte Carlo techniques to compute the transport and surface kinetics combined with a cellular representation of the feature. The Monte Carlo algorithm permitted the incorporation of all the dominant physical and chemical mechanisms of the etching process such as angle-dependent ion-enhanced etching, physical sputtering, ion scattering, surface recombination, plasma deposition, sidewall passivation, and line-of-sight redeposition without encountering numerical difficulties. The technique allows for the modification of surface kinetics rates based on the surface composition. Simultaneous composition-dependent etching and deposition could be handled easily. A modification of the cellular representation of the feature (similar to a string-and-node algorithm) was developed to determine neutral species interactions with the surface enabling accurate simulation of deposition processes. A surface normal calculation algorithm involving least-squares fitting of the surface was developed to handle specular ion scattering. A generalizable structure allowing the incorporation of all chemical and physical processes was developed to handle the compositional, energy, and angular dependent surface processes. Test cases were run to quantify the accuracy of the combined Monte Carlo and cellular algorithms.
For adequate transparency we have selected hexafluoroisopropanol as an acid group and an ␣-trifluoromethylacrylic moiety as a repeat unit of our 157 nm resist polymers. The hexafluoroalcohol group is bound to norbornene or styrene. Four platforms are currently available to us: ͑1͒ all-acrylic, ͑2͒ all-alicyclic, ͑3͒ acrylic-alicyclic, and ͑4͒ acrylic-aromatic systems. While the all-alicyclic ͑all-norbornene͒ polymers are synthesized by transition-metal-initiated addition polymerization, all other polymers involving ␣-trifluoromethylacrylic monomers are prepared by conventional radical copolymerization. Characterization of the polymers and preliminary lithographic evaluation are reported.
For a range of applications, polymers are now being patterned into nanometer‐sized features. In these applications, the robust mechanical properties of the nanostructures are critical for performance and stability. Brillouin light scattering is presented as a nondestructive, noncontact tool used to quantify the elastic constants in such nanostructures. We demonstrate this through a series of thin films and parallel ridges and spacings (gratings) with ridge widths ranging from 180 to 80 nm. For the set of films and structures presented here, the room‐temperature elastic moduli did not change with decreasing film thickness or grating ridge width, and this implied that one‐dimensional and two‐dimensional confinement‐induced changes of the mechanical properties were not significant down to feature sizes of 80 nm. Additionally, Brillouin spectra of submicrometer gratings revealed new modes not present in the spectra of thin films. The origin of these new modes remains unclear. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1106–1113, 2004
Chlorine-based plasma etching of polysilicon was characterized as a function of the impinging Cl+, Cl–to–Cl+ flux ratio, ion bombardment energy, ion bombardment angle, and the flux of etching by-products (SiCl2) using a multiple beam scattering apparatus. The ion-enhanced etching yield was a strong function of the neutral-to-ion flux ratio, and scaled linearly with the square root of the ion energy. The ion-enhanced etching yield was independent of the ion bombardment angle at near normal ion incidence angles, but decreased almost linearly above 40° off-normal angles. The presence of SiCl2 greatly suppressed the etching of polysilicon by either Cl+ or Cl+ with Cl. A Monte Carlo based profile simulator was constructed which incorporated the dominant reaction mechanisms of surface chlorination under ion bombardment, surface re-emission, and ion reflection. The profile evolution of patterned samples etched by Cl and Cl+ beams were simulated. Quantitatively good agreement was found between the simulated profiles and the measured profiles. A sensitivity analysis of the recombination probability of Cl on photoresist suggested that the recombination of atomic chlorine on the photoresist had a significant impact on the profile evolution.
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