EUV Resists Research Articles

Photoresist Design to Address Stochastics Issues in EUV Resists

Photoresist Design to Address Stochastics Issues in EUV Resists

Comparison of Photoresist Sensitivity between KrF, EB and EUV Exposure

It has been reported that the good correlation in sensitivity and resolution between EUV exposure and EB exposure because of the similar mechanism of the photochemical-reaction in photoresists during exposure. However, in the early stages of EUV resist development, there are problems on the points of the cost and time-consuming to evaluate all EUV resist materials by EB exposure. Therefore, we investigated the possibility of using KrF exposure as the initial screening of EUV resists. If the correlation between KrF exposure, EB exposure and EUV exposure can be found, it will be possible to evaluate photoresists in a step-by-step manner, such as screening with KrF exposure first, followed by EB exposure, and finally EUV exposure in the initial evaluation stage. In this paper, we report on our investigations in the case of novolac resists, PHS chemically amplified resists, acrylic chemically amplified resists, and EUV polymer resists.

Grazing-Incidence Soft-X-ray Scattering for the Chemical Structure Size Distribution Analysis in EUV Resist

In extreme ultraviolet lithography (EUVL), it is required to develop EUV resist which has low line width roughness (LWR) for the further miniaturization of circuit pattern. In order to reduce LWR, it is necessary to analyze and control the chemical-components spatial distribution in the resist thin film. We have reported that the measurement of chemical-components spatial distribution in the resist thin film coated on the Si3N4 membrane using the method of the transmission-mode resonant soft X-ray scattering (RSoXS). In this study, in order to analyze the chemical-structure-size distribution in the resist thin film on a Si wafer under similar condition adapted to the resist-coating actual process, we examined the grazing-incidence RSoXS (GI-RSoXS). A chemically amplified resist (CAR) and a non-CAR were spin-coated on silicon wafers, which had varied film thickness of 20, 50, and 100 nm. The scattering profile of each sample was measured at the incident photon energy of 280 and 296 eV. As a result, it is suggested that the chemical-structure-size distribution in the resist thin films depends on the resist film thickness. It is confirmed that the GI-RSoXS method is very effective to evaluate the chemical-structure-size distribution of resist thin films.

Stochastic Modeling and Local CD Uniformity Comparison between Negative Metal-Based, Negative- and Positive-Tone Development EUV Resists

Stochastic Modeling and Local CD Uniformity Comparison between Negative Metal-Based, Negative- and Positive-Tone Development EUV Resists

Study of EB Resist Simulation for EUV Resist Evaluation

Study of EB Resist Simulation for EUV Resist Evaluation

Stability studies on a sensitive EUV photoresist based on zinc metal oxoclusters

Background: Hybrid inorganic-organic materials have emerged as promising candidates for EUV resists. However, knowledge on their stability when deposited as thin films is essential for their performance in EUV lithography. Aim: We investigate whether the molecular structure of Zn-based metal oxoclusters is preserved upon thin film deposition and study aging processes of the thin film under different atmospheres, since these chemical changes affect the solubility properties of the material. Approach: A hybrid cluster that combines the high EUV photon absorption cross-sections of zinc and fluorine with the reactivity of methacrylate organic ligands was synthesized. The structural modifications upon thin film formation and after aging in air, nitrogen, and vacuum were studied using a combination of spectroscopic techniques. Preliminary studies on the lithographic performance of this material were performed by EUV interference lithography. Results: The Zn-based compound undergoes structural rearrangements upon thin film deposition as compared to the bulk material. The thin films degrade in air over 24 h, yet they are found to be stable for the duration and conditions of the lithography process and show high sensitivity. Conclusions: The easy dissociation of the ligands might facilitate hydrolysis and rearrangements after spin-coating, which could affect the reproducibility of EUV lithography.

Resonant Soft X-ray Scattering for the Stochastic Origin Analysis in EUV Resist

Resonant Soft X-ray Scattering for the Stochastic Origin Analysis in EUV Resist

Resonant Soft X-ray Reflectivity for the Chemical Analysis in Thickness Direction of EUV Resist

Resonant Soft X-ray Reflectivity for the Chemical Analysis in Thickness Direction of EUV Resist

Characterization Studies on Metal-based EUV Resist Film Properties

Characterization Studies on Metal-based EUV Resist Film Properties

Novel EUV Resist Materials for 7 nm Node and Beyond

Novel EUV Resist Materials for 7 nm Node and Beyond

Fabrication of High-Aspect-Ratio Transmission Grating Using DDR Process for 10-nm EUV Resist Evaluation by EUV Interference Lithography

We have developed an EUV interference lithographic exposure tool to evaluate a resist. The target patterning size of this system is 10 nm and below in half pitch. Transmission grating fabrication is a key technology in EUV interference lithography. To replicate a 10-nm-line-and-space (L/S) resist pattern on a wafer, a 20-nm-L/S pattern is required for the transmission grating. The pitch size of the interference fringes is half the size of the absorber pattern of the transmission grating. For the chemically amplified positive tone resist process, instead of alkali development, organic development can be adopted to convert to a negative-tone chemical amplification resist process, and pattern collapse can be suppressed. In addition to this process, a dry development rinse (DDR) process is used. The DDR process with dry development successfully prevents pattern collapse at a high aspect pattern because there is no surface tension in the dry development of the DDR process. The EUV diffraction efficiencies of the fabricated gratings were measured to be 14%, 11% and 4% for 40, 30 and 20-nm-L/S pattern grating, respectively. Using these gratings, 20, 15 and 10 nm resist pattern might be replicated on a resist. And the diffraction efficiency was sufficient for interferometric exposure using synchrotron radiation.

Understanding Extreme Stochastic Events in EUV Resists

Author(s): Naulleau, P; Bhattarai, S; Neureuther, A | Abstract: The problem of stochastics in photoresist patterning is of significant concern in the commercialization of extreme ultraviolet lithography, especially in patterning of contacts or vias. Traditionally, contact hole critical dimension (CD) variability is characterized as a Gaussian process, however, recent experimental results have demonstrated significant deviations from Gaussian statistics, especially on the small CD side. Modeling results show that this non-Gaussian variation is expected and can be attributed to the non-linear behavior of the contact hole exposure latitude as a function of dose. It is shown that if we consider the noise in the dose or sensitivity domain, it can still be treated as a Gaussian process. The CD statistics are then determined by mapping the Gaussian dose/sensitivity noise through the non-linear and deterministic CD versus dose function.

In-situ Measurement of Outgassing Generated from EUV Resist Including Metal Oxide Nanoparticles during Electron Irradiation

In this study, we evaluated the outgassing generated from EUV resist which included metal oxide nanoparticles during electron irradiation. We prepared two types of samples including ZrO2 and TeO2, and a sample without including metal oxide, respectively. The outgassing species were measured from each sample during electron irradiation at the Eth exposure dose. The electron acceleration energy was 2 keV. In the outgassing measurement, we used original in-situ outgassing monitoring system in quadrupole mass spectrometry which we developed. From the results of mass spectrum, we observed CO2, H2O as typical mass peaks at each sample. And also we observed C4H4O2 and C4H6O2 peaks in spectrum of each sample. And these peaks are guessed 2(5H)-furanone and butyrolactone generated from base polymer. C6H6 peaks were observed in the mass spectrum of including ZrO2 and TeO2. We guessed that these peaks are from benzene generated from photo-acid generator (PAG). On the other hand, C6H6 peaks were not observed in the mass spectrum of without metal oxide. About this, we could not explain that mechanism by our knowledge of the present, but we can guess that metal oxide nanoparticles worked to generate benzene. About metal oxide peaks did not observe about mass spectrum of each sample. Each metal or metal oxide might not be evaporated during electron irradiation.

Metal Sensitizer in Chemically Amplified EUV Resist: a Study of Sensitivity Enhancement and Dissolution

Metal Sensitizer in Chemically Amplified EUV Resist: a Study of Sensitivity Enhancement and Dissolution

Absorption Coefficient Measurement Advanced Method of EUV Resist by Direct-Resist Coating on a Photodiode

Absorption Coefficient Measurement Advanced Method of EUV Resist by Direct-Resist Coating on a Photodiode

EUVレジストの高感度化の検討

EUVレジストの高感度化の検討

Sequential Infiltration Synthesis for Line Edge Roughness Mitigation of EUV Resist

It is well known that high line-edge roughness (LER) and line-width roughness (LWR) are one of the key problems hindering utilization of extreme ultraviolet lithography (EUVL) in fabrication of semiconductor devices at advanced technology nodes where pattern with sub-20 nm half pitch lines and spaces is required. Sequential infiltration synthesis (SIS) has never been used before in lithography for line-edge roughness mitigation, but this concept has proved its value for 14 nm half pitch block copolymer lines formed by directed self-assembly. During this process an inorganic scaffold is being deposited inside the resist material after performing several sequential infiltration cycles with metal-organic precursor and its oxidizing agent. Etching in oxygen atmosphere after is required to transform former resist pattern into metal oxide one and improve (up to 40%) the pattern roughness. In this paper, for the first time we demonstrate feasibility of sequential infiltration synthesis (SIS) for smoothing of EUV resist lines.

Development of the Transmittance Measurement for EUV Resist by Direct-Resist Coating on a Photodiode

Development of the Transmittance Measurement for EUV Resist by Direct-Resist Coating on a Photodiode

Enabling EUV Resist Research at the 1x and Smaller Regime

Author(s): Naulleau, P; Anderson, C; Chao, W; Goldberg, K; Wojdyla, A; Bhattarai, S; Neureuther, A; Goodwin, F; Neisser, M | Abstract: With the slipping of the insertion node for extreme ultraviolet lithography, demands on resist resolution have increased further stressing sensitivity requirements. A variety of resists, both chemically amplified and not, have been developed meeting resolution needs, but falling short on sensitivity and line-width roughness (LWR). Note that resolution is an absolute mandatory requirement, the true tradeoff that must be considered is between sensitivity and contact hole printing is a crucial application for extreme ultraviolet lithography and is particularly challenged by resist sensitivity due to inherent inefficiencies in darkfield contact printing. Checkerboard strong phase shift masks have the potential to alleviate this problem through a 4× increase in optical efficiency. The feasibility of this method is demonstrated using the SEMATECH-Berkeley Microfield Exposure Tool pseudo phase shift mask configuration and preliminary results are provided on the fabrication of an etched multilayer checkerboard phase shift mask.

Novel EUV Resist Materials Design for 14 nm Half Pitch and below

Novel EUV Resist Materials Design for 14 nm Half Pitch and below