ECLIPSE: GOALI: Electron Beam Induced Atomic Layer Etching for Atomic Scale Processing of Materials

University Of Maryland, College Park, College Park MD

Investigators

Abstract

During manufacturing of current semiconductor and related industry products, atomic precision in materials etching is required. Plasma-based atomic layer etching (ALE) provides a solution to achieve precise target dimensions and material selectivity by using ion-bombardment. Damage due to ion-induced mixing and atomic displacement has become an important concern for devices with near-atomistic critical dimensions. This Ecosystem for Leading Innovation in Plasma Science and Engineering (ECLIPSE) Grant Opportunity for Academic Liaison with Industry (GOALI) award supports fundamental research to obtain the required knowledge for the development of the electron beam activated atomic layer etching (EB-ALE) process which avoids ion induced atomic displacement and damage. A plasma source that is spatially distant from the substrate chemically modifies the material surface. This is followed by electron beam irradiation induced etching restricted to the modified surface. The novel EB-ALE approach enables layer-by-layer etching for critical applications involving complex multi-element materials that are extremely sensitive to process damage. The application of EB-ALE for processing of advanced materials and structures benefits the US economy and society by wide-ranging impacts on advanced manufacturing for microelectronics, quantum technology, renewable energy, electrical storage applications, and others. The academic and industrial collaboration provides unique educational and training opportunities for the students, faculty and researchers involved, including women and underrepresented minorities, and accelerates technology transfer. Electron-beam induced atomic layer etching (EB-ALE) of materials is based on surface functionalization using a remote plasma source, and subsequent electron beam-irradiation of the modified surface. Electron bombardment induces bond breaking processes and achieves self-limited etching while avoiding ion-induced displacement damage connected with direct plasma based atomic layer etching methods. This project aims to make fundamental contributions to the knowledge gap in understanding surface chemical and physical aspects of EB-ALE mechanisms by combining surface processing experiments using selected precursors/substrate materials and in-situ diagnostics. Maintaining stoichiometry is vital for advanced materials, such as, Ge2Sb2Te5 phase change memory alloys. Dissociation of precursor gases in the remote plasma source and transport to the material surface are studied for different operating conditions, including remote plasma power, gas flow rates and mixing, and correlated with the measured surface coverage. Etching behavior is established as a function of electron beam current density and energy, surface chemical modification and coverage and device structure. The relative importance of electrical charging is examined by evaluating insulators and conductors for different electron beam irradiation conditions. The nature of surfaces and defects of model complex materials after EB-ALE is established using an array of sensitive analytical and electrical probes. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.