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Application of Organic Silicon Clusters to Pattern Transfer Process for Deep UV Lithography

A pattern transfer process using organic silicon clusters (OSCs) as bottom antireflective coating (BARC) for deep UV (DUV) lithography is introduced to realize high antireflective performance and efficient etch properties simultaneously. Unlike linear polysilanes, OSC has three-dimensional quaternary Si atoms (cluster units called Q units). It can be simply spin-coated and lowers the cost of ownership. Its refractive index at 248 nm is n=1.80 and k=0.30, and the intrinsic reflectivity is greatly reduced to 0.6%. Etch selectivity of BARC/resist is 3.3, which is much higher than that of the conventional organic BARC, namely, ∼1. OSC can also act as an adequate etch mask: etch resistance is 1.1 times greater than that of the resist and it is not denatured during substrate (dielectrics) etching. In comparison with the conventional organic BARC process, the OSC's excellent etch properties reduce resist thickness required to etch a substrate by approximately 270 nm, which enlarges the lithographic process window.