Caracterização do estresse mecânico de nanoestruturas de silício tensionado por espectroscopia Raman

Author(s)

Lucas Barroso Spejo

• Document type: Master's Dissertation
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Engenharia Elétrica e de Computação
• Defense date: 2020-03-12

Examining board members

José Alexandre Diniz; Ricardo Cotrin Teixeira; Leandro Tiago Manêra

• Advisor: Marcos Vinicius Puydinger dos Santos; José Alexandre Diniz

Abstract

Strained silicon engineering has proven to be a successful technology to keep Moore¿s law and presents a great potential for its use in even smaller and highly stressed technological nodes in microelectronics in the future. Such a task demands the use of stress characterization techniques for semiconductor research and development. One potential characterization tool which makes possible quantitative stress measurement of silicon is the Raman spectroscopy. This characterization method is a wellestablished non-destructive technique that permits stress characterization with a spatial resolution of below 1 ?m and does not require complex sample preparation procedure. However, studies on Raman shift behavior of highly stressed structures (stress greater than 2 GPa) with the critical dimension smaller than 100 nm are scarce in the literature, being a bottleneck for the systematic use of Raman measurements in future technological devices. Here, it was investigated the Raman shift-stress behavior from the (001) silicon surface of highly strained ultra-thin (15 nm-thick) suspended nanowires with stresses in the range of 0 ¿ 6.3 GPa along the [110] direction. The use of ultrathin nanowires as a platform of study, along the [110] crystallographic direction, allowed the systematic investigation of one essential block that might be present in future nMOS transistors channels. Furthermore, this suspended platform reached ultra-high stress values (up to 6.3 GPa) without external actuators, allowing for the first time the systematic study of the Raman stress behavior of highly stressed nanowires. The stresses were evaluated by finite element method (FEM) simulations to achieve great accuracy in the stress characterization. Then, experimental Raman measurements were performed, followed by a thermal correction protocol to extract the corrected Raman peak free of thermal effects. The extracted stress shift coefficient (SSC), for lower stresses (below 4.5 GPa), was in good agreement with some of the SSC values in literature. For higher stresses (greater than 4.5 GPa), it was demonstrated, for the first time, that the linear shift Raman - stress relation does not hold, thus requiring an empirical model correction proposed in this work. The results demonstrate the feasibility of the Raman technique for the stress characterization of ultra-thin silicon nanowires, which should be useful to characterize strained silicon nanodevices for technological nodes below 100 nm under a wide range of stresses, contributing to such an important topic in the semiconductor industry (AU)

• FAPESP's process: 18/02598-4 - Giant Piezoresistance and electrical carriers mobility of ultra-strained silicon nanowires
• Grantee: Lucas Barroso Spejo
• Support Opportunities: Scholarships in Brazil - Master