Investigation of FIN Bowing Formation Mechanism During STI Etching by Virtual Fabrication

Shallow trench isolation (STI) etch is the process used to form fin channel structures in logic FinFET devices. Fin bowing is a common and key challenge during the STI etch process, especially for advanced nodes with higher aspect ratio. In this study, a virtual STI etch process was established and calibrated using the SEMulator3D
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platform by Coventor Inc. A virtual design of experiments (DOE) revealed that ion angular distribution function (IADF) and hard mask (HM) profile taper are two key factors that induce a bowed fin profile. Wide ion angle distribution causes direct ion impingement at the sidewall, and a tapered HM profile will create ion scattering that bombards the adjacent fin sidewall. Both mechanisms result in fin bowing. In this study, we explored process trends and sensitivities of IADF, HM angle, HM height and space CD on fin bowing. Our results provide guidance on fin bowing profile reduction optimization, including enhanced sidewall passivation and implications on etch tool and hardware selection that impact ion distribution angle control and HM profile optimization.