The application of the ethyltrimethylammonium hydroxide (ETMAH) as alternative developer solution for EUV lithography was investigated (compared to the tetramethylammonium hydroxide or TMAH standard developer). Early reports have shown that at a specific or optimal developer concentration of around 0.20N the ETMAH developer allows mitigation of resist-based stochastic defects (increase in stochastic defect margin) while maintaining lithographic performance. Results obtained here suggest that with the use of a non-ionic surfactant additive for the ETMAH developer solution LWR reduction was achieved (compared to TMAH). This improvement in LWR was achieved while preserving resolution, sensitivity, and stochastic defect margin.
Currently, there are many developments in the field of EUV lithography that are helping to move it towards increased high volume manufacturing (HVM) feasibility. Targeted improvements in hardware design for advanced lithography are of key interest to our group, specifically metrics such as line width roughness (LWR) smoothing, dose reduction processes, and defect mitigation. In this study, we investigate how novel hardware solutions currently available on our SCREEN DT-3000 coat-develop track system, can be used as complementary non-patterning approaches to boost resist scaling even further. The utility of SCREEN non-standard hardware features to enhance overall lithography performance of a main chain scission EUV resist was deeply explored, and new process approaches were successfully identified. We hereby present our work utilizing the SCREEN DT- 3000 coat-develop track system with an ASML NXE:3400 to improve sensitivity, CD uniformity, line width roughness, and defectivity levels of aggressive dense L/S patterns.
As the next generation of Extreame Ultraviolet (EUV) lithography, high-NA EUV is proposed. EUV resist is one of the challenges to achieve it. Non-CAR type hemicellulose resist was proposed last year and improved for high-NA EUV resist. The target is stable and high resolution chain scission resist. It was confirmed that hemicellulose works as a radical source by electron spin resonanse(ESR) analysis and hemicellulose improves EUV sensitivity from 50 to 28 mJ/cm2. The primary advantage of the hemicellulose resist is its excellent wafer transportability. The properties of resist such as low metal contamination, resist film uniformity, and edge cut were confirmed. The optimization of the lithography process improves the resolution of hemicellulose resist and pitch 26 nm L/S pattern was obtained with OPALTM-RH02. Furthermore, hole pattern of pitch 40 nm was also obtained.
Extreme ultraviolet (EUV) lithography is a candidate for the manufacturing of semiconductor devices at the 22 nm half pitch node and below. EUV lithography requires high performance resist with limited outgassing property. The key challenge for EUV resist is the simultaneous requirement of ultrahigh resolution (R), low line edge roughness (L) and high sensitivity (S) for lines and spaces (LS) features. To achieve high resist sensitivity EUV resist absorbance should be increased. Resin containing fluorine atom is one of the most attractive methods to improve absorbance level of EUV resist because the fluorine atom absorbs EUV light strongly. However, resist hydrophobicity (or high contact angle) also increase due to presence of fluorine atoms in the resist polymer. It is difficult to rinse high CA resist during development process so the resist containing polymer with fluorine atom may produce additional defects. In this paper, we will report the relationship between line edge roughness and acid diffusion length. We will also show the method to diminish defects caused by high contact angle (CA) resist. We achieved good resolution and LER improvement by controlling acid diffusion length. Moreover, we found the relationship of the number of defects and the structure of the monomers containing fluorine units.