Metal Oxide Resistant (MOR) EUV Lithography Processes for DRAM Application

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This article reports on the readiness of major EUV resistor process technologies using metal oxide resistor (MOR) aimed at DRAM application. For MOR, reduction of metal contamination and uniformity of CD (CDU) are the main performance requirements expected regarding post-exposure bake (PEB). Based on years of experience with the Inpria MOR type spin-on, we have designed a new PEB furnace to achieve contamination mitigation, while maintaining our high CDU level. The new baking oven was introduced to our coater and developer and evaluated using line/space models. As described in the results, exceptional CD uniformity was achieved while exceeding the metal contamination specification. The new plate design also allowed a 30% reduction in dose-size ratio without CDU degradation when applying a higher PEB temperature. Another challenge for the DRAM application in particular is pattern collapse as applied to pillar patterns. By optimizing several parameters, the pattern collapse margin extended the CD minimum by 13.8%. The result was achieved with a combination of SiC instead of SOG for the underlayer, a thinner resist film thickness, and a modified resist material, MOR-B. Finally, to achieve the target yield performance, defectivity reduction is also an important task towards the MOR application. An integrated approach is required to achieve scum-free patterning because if metal residue remains in the open space, it can cause yield-destroying defects. By analyzing the possible root causes of defect sources, we attempt to eliminate the etch masking scum layer present after conventional developer processing. By applying a post-development rinse including a new material for defect reduction, bridge defects were reduced by up to 19% with the new technology.

Authors: Shinichiro Kawakami,1 Tomoya Onitsuka,1 Youya Kamei,1 Satoru Shimura,1 Chan Ha Park,2 Sang Ho Lee,2 Hong Goo Lee,2 Jae Wook Seo,2 Jin Il Kim,2 Jun ho Roh,2 Jin Hyung Kim,2 Ki Lyoung Lee,2 Seiji Nagahara,3 Jeung Yun Kim,4 Jang Hwan Kim,4 Shingo Inaba,5 Jong Eun Park4

1Tokyo Electron Kyushu Ltd. (Japan)
2SK Hynix, Inc. (Korea, Republic of)
3Tokyo Electron Ltd. (Japan)
4Tokyo Electron Korea Ltd. (Korea, Republic of)
5Tokyo Electron Korea Ltd. (Japan)

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