The improvement of EUV photoresists is a key enabler for the deployment of High-NA EUV lithography and future technology nodes. Research in this field is supported by a joint research program between PSI and ASML. This program is dedicated to supporting the EUVL community with the development of materials by carrying out resist screening experiments with the EUV interference lithography tool at PSI, with an emphasis on resolution improvement towards reaching High-NA EUV scanner specifications. The tool enables high-resolution patterning without limitations in terms of chemical outgassing or contamination and is, therefore, an effective method for the testing of novel EUV photoresists. In this work, we consider the progress monitored in the second half of 2021. We describe the exposure tool as well as the updates made to the resist characterization metrology implemented at PSI. Resist performances are quantified with regards to resolution, linewidth roughness, and sensitivity. We show an overview of the current development status through a comparative study of different resist platforms. Recent results show chemically amplified resists (CAR) and non-CAR printing 12 nm and 11 nm lines/spaces features, respectively. Limitations of each platform are displayed and general progress and perspectives are discussed to lead the way to higher resolution results.
The introduction of novel photoresists is a critical enabler of future technology nodes, including the upcoming high-NA EUVL deployment. The development of EUV materials is investigated within the scope of a resist screening program between ASML and PSI. In this work, the EUV interference lithography tool at PSI is used to study materials performance in terms of the resolution-roughness-sensitivity tradeoff, with an emphasis on ultimate resolution. Here, we review the development status of different platforms by considering recent results obtained in the first half of 2021 (H1-2021). Patterning resolution of 11 nm half-pitch is achieved with both CAR and non-CAR materials, which indicates steady progress in the global resist development. Perspectives of this work are discussed towards enabling 8 nm half-pitch resolution solutions.
As EUV lithography becomes the new standard for electronic chip manufacturing, identifying suitable materials for higher resolution patterning stands out as a prominent challenge to reach future technology nodes. Innovative approaches to patterning are becoming more and more relevant as conventionally used photoresists approach their limitations. In this work we use the Interference Lithography tool at the Paul Scherrer Institute (Swiss Light Source) for screening of EUV Lithography materials. We highlight the EUV lithography exposure mechanism of secondary electron chemistry and its versatility in inducing a solubility switch in photosensitive materials by using a chicken egg-white albumin protein cluster as a resist to obtain sub-100 nm patterns.
The development of EUV resists is one of the major challenges for the deployment of high-NA EUV lithography, which is on the roadmap for high-volume manufacturing of future semiconductor technology nodes. Resist performance is admittedly governed by a resolution-roughness-sensitivity (RLS) tradeoff. This study reports on the EUV resist progress achieved during the last year in the framework of the resist screening program by PSI and ASML. An extensive performance characterization of different resists was carried out using the XIL-II beamline EUV interference lithography (EUV-IL) tool at the Swiss Light Source (SLS). We present the upgraded screening metrology used in 2020 at PSI enabling increased confidence in results. We report material performance towards patterning lines/spaces features with respect to the key parameters of RLS: half-pitch (HP), dose-to-size (DtS), line-width-roughness (LWR), as well as Z-factor for overall performance consideration. General progress in EUV resist development is reviewed by considering several resist platforms available today from different vendors. Different molecular and chemically amplified resist materials are demonstrated as viable for 16 nm resolution technology nodes. One chemically-amplified resist vendor shows suitable materials for 13-nm-resolution technologies while exhibiting potential for further downscaling. We present different metal-oxide resists screening with resolutions down to 10 nm HP. We finally discuss the overall progress of materials achieved between 2019 and 2020 towards reaching high-NA.
High-NA extreme ultraviolet lithography (EUVL) is going to deliver the high-volume manufacturing (HVM) patterning for sub-3nm technology node for the semiconductor industry. One of the critical challenges is to develop suitable EUV photoresists at high resolution with high sensitivity and low line-width roughness (LWR) at reduced film thickness needed for high-NA by its reduced depth of focus (~1/NA2). The resist performance is generally limited by the resolution-LWR sensitivity (RLS) tradeoff, and it is critical to find new materials to support the future lithography nodes. EUV interference lithography (EUV-IL) is a powerful and efficient technique to test new materials at high resolution. In this work, we evaluate the performance of about 120 EUV resists, including molecular resist, inorganic resist, chemically-amplified resist (CAR), and chemically-amplified resist with a metal sensitizer (metal-CAR). Among all tested resists, we selected and compared six resists with the best performance in dose-to-size, line-width roughness, and maximal exposure latitude for 16 nm and 14 nm half-pitch (HP) lines/spaces (LS). A molecular resist showed the lowest dose to resolve HP 16 nm (29 mJ/cm2) and 14 nm (31 mJ/cm2), still featuring low LWRunbiased (2.7 nm and 3.1 nm, respectively). We observed that there is steady progress in EUV resist development: the LWR of the resists was improved in comparison with the results of the last two years as we noted that the amount of the resists within given dose and LWR threshold increased from 10 % to 33% for HP 14 nm. For contact holes, CAR gave the lowest LCDU of 2.2 nm for HP 20 nm with the lowest doses (21.1 mJ/cm2). While inorganic resists resolved pillars with highest resolution HP down to 18 nm with LCDU of 2.1 nm.
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