LWR Improvement Research Articles

The Line Roughness Improvement in Self-aligned Multiple Patterning

Multi-patterning has been widely used in the semiconductor industry to enable the continued scaling requirement such as Fin, Gate, and critical Metal lines. Either Self-aligned Multiple Patterning (SaMP) or Litho-Etch/Litho-Etch (LELE) shows plasma etch become more dominant for the line edge and width roughness (LER/LWR) than single patterning technology [1]. To mitigate the strict line roughness requirements for advanced technology nodes (14nm and below), we proposed and demonstrated a novel nitrogen-based Inductively Coupled Plasma (ICP) treatment and an argon-based Capacitively Coupled Plasma (CCP) treatment on LER/LWR improvement, separately. Both recipes are optimized with an optimal design experiment (ODE) statistical method. The optimal organic mandrel etch recipe can improve the LER of the final pattern to 1.2nm. Furthermore, two effective Si mandrel post etch treatment (PET) methods are investigated: special surface plasma treatment and H2 anneal. The H2 anneal effect was found related to the capping layer, different from former published paper. We also found out the different chemistry in Spacer etch can impact line roughness but trade-off with defect performance. Finally, we achieved a 20% LWR improvement of final pattern in a self-aligned quadruple patterning (SAQP) without any side effect.

Materials challenges for sub-20-nm lithography

We discuss the future of resist materials for sub-20-nm lithography and believe that polymer-bound PAG-based resists will be used to 16-nm node. There has been enough progress in resolution and sensitivity to justify the use of these materials. Polymer-bound PAG resists have shown that the principal demerit of acid diffusion can be overcome through attachment of the PAG anion to the lithographic polymer. Since the introduction of this chemically amplified resist approach, we have seen steady improvement in resolution, sensitivity, and LWR. We have also seen improvement in OOB response, outgassing, and pattern collapse. There is no doubt that continuous improvement is still required for these resist systems. We believe that increasing the overall resist quantum yield for acid generation substantially improves the shot-noise problem thereby leading to faster high-resolution resist materials. Using a 0.30-NA extreme ultraviolet tool with dipole, we can achieve 22-nm hp resolution, with a 12-mJ dose and a 4.2-nm LWR.

Optimization of Polymer-bound PAG (PBP) for 20nm EUV Lithography

This paper discusses the continued evolution of Polymer-bound PAG [PBP] resists for sub-20nm lithography. Utilizing EUV wavelength, there has been enough progress in resolution and sensitivity to justify the use of these materials. PBP resists have shown that the principal demerit of acid diffusion can be overcome through attachment of the PAG anion to the lithographic polymer. Since the introduction of this chemically amplified resist approach, we have seen steady improvement in resolution, sensitivity, and LWR. Using a 0.30NA EUV tool with dipole, we can achieve 22nm hp resolution, with 12mJ dose, and 4.2nm LWR. Through rational PAG cation design, we have substantially reduced to a factor of 1/10th the PBP resist response to Out-of- Band Radiation compared to a TPS-based PBP. In this way, the resist can act as in situ spectral filter for unwanted longer wavelength exposure.

JSR EUV Resist Development toward 22nmhp Design and Beyond

In order to achieve targeted resist performance for EUV in practical applications, we have developed new materials such as molecular glass (MG), PAG, and acid amplifiers (AA). Protected NORIA, a molecular glass, was examined for extending resolution limits. The resist with protected NORIA showed 22 nm hp resolutions under EUV exposure. PAG acid diffusion effect on LWR was also investigated. It was found that acid diffusion control was one of the most important factors for LWR improvement. To improve sensitivity, application of AA (acid amplifier) was investigated. The resist with AA gained 25% sensitivity improvement over the original formulation. Elemental technologies for major progress of EUV resist were made.

A Resist Material Study for LWR and Resolution Improvement in EUV Lithography

It had been reported that LWR and resolution were improved according to loading amount of quencher along with a decrease of sensitivity. Influences of quencher and PAG anion size on acid diffusion in acetal protected PHS-based polymer were examined and it was found that acid diffusion length is mainly controlled by quencher, resulting in the improvement of LWR and resolution as well as the decrease of sensitivity by way of reducing acid diffusion length. In order to compensate for the sensitivity loss, we investigated the effect of PAG structures and properties on acid generation and it was found that acid generation efficiency increased with the reduction potential of PAG. In this paper, we discussed how to solve the dilemma among sensitivity, resolution and LWR in EUV lithography, by applying high-efficiency PAG under high quencher concentration.

Reduction of the Outgassing Segments and LWR Improvement for the Next Generation EUV Lithography

The continuous studies for both the outgassing reduction and the sensitivity improvement by applying low outgassing photo acid generator with a various kinds of polymer protection group were discussed in this paper. Further reduction of the outgassing segments from the resist was demonstrated to achieve the total outgassing amount below the detection limit of GC-MS (ca. less than 1X1010 molecules / cm2). Loading a large sized acetal group could be successfully reduced the amount of the outgassing segments from polymer below the tool detection limit, which would be acceptable for a high volume manufacturing tool usage. The development properties of poly(hydroxyl styrene) (PHS) based bulky acetal polymers were measured by changing molecular weight. The high dissolution rate contrast was obtained with the bulky acetel protected low molecular weight polymer. A resolution capability study was carried out with micro exposure tool (MET) at LBNL and Albany. The correlation between LWR through CD and DOF was measured by loading various amounts of quencher. The resolution capability of newly developed EUV resist had been successfully improved by modifying both resist polymer matrix and quencher amount optimization. It was possible to obtain 27.7nm lines with MET tool, where LWR value at 35 nm L/S was 3.9 nm with reasonable sensitivity range.

Development of the demonstration FBR and its commercialization

The FBR being developed in Japan is expected to operate commercially by the year 2030 or so. The construction of the first demonstration FBR “DFBR-1”, which follows the experimental FBR “JOYO” and the prototype FBR “MONJU” is scheduled for early 2000s. The Atomic Energy Commission adopted these policies in the new version of “The Long Term Program for Research, Development and Utilization of Nuclear Energy”. The Japan Atomic Power Company has progressed design studies of the DFBR-1 and R&Ds. Electric utilities settled the major design specifications of the DFBR-1 such as the top entry loop type as the reactor type and about 660 MWe of plant capacity. To achieve the goals for the commercialization of FBRs, such as a high level of safety and reliability comparable with a LWR and further improvement of economy, many innovative technologies and system improvements will be required in commercial FBRs. This paper describes the present status of development of the DFBR-1.

RD & D for improving reliability of Japanese nuclear power plants

Abstract Research, development and demonstration of the technologies relating to improvement of nuclear power plant reliability in Japan are characterized by: (1) emphasis on public acceptance; (2) engineering philosophy of preventive maintenance; (3) execution of thorough countermeasures for improvement. Utilities and vendors are basically responsible for RD&D in this commercially established area. However, the government is also involved in safety related and other important items, and most of these activities are conducted under good coordination between government and private sectors. The government, more specifically, the Ministry of International Trade and Industry (MITI) is conducting various reliability proving and verification tests reaching the scale of 12 billion yen (50 million US dollars) in annual average. In close cooperation with industry MITI is also promoting sophistication of LWR technologies such as development of advanced LWR's and improvement of inspection, maintenance and operation, without being satisfied with the recent good records of nuclear power plant operations.