Rapid Thermal Processing and its Effects on High Aspect Ratio Silicon Features

• Autor(a) principal: Diogo, Inês Rodrigues
• Data de Publicação: 2022
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositórios Científicos de Acesso Aberto de Portugal (RCAAP)
• Texto Completo: http://hdl.handle.net/10362/152031
• topic: Rapid thermal processing; argon anneal; hydrogen anneal; surface atom migration; SON structures; 3D profile transformation; Domínio/Área Científica::Engenharia e Tecnologia::Outras Engenharias e Tecnologias

Silicon (Si) is the most widely used material in semiconductor devices fabrication, and silicon wafers undergo many steps before achieving the final product, including heat treatments. A rapid thermal processor, with a base pressure of 10-6 mbar, is the case study of this work, and it’s proposed as an alternative to more conventional furnace methods. Moreover, the main goal was to investigate the impact rapid thermal processing (RTP) has on different high aspect ratio (HAR) structures etched into Si substrates. The ‘clear – oxidize – remove – etch’ (CORE) process was used as the primary etching process, resorting to a deep reactive ion etching (DRIE) tool. The structural characterization was mainly carried out by scanning electron microscopy, although ellipsometry has also been used. RTP refers to any process that implies elevating the temperature of a given material, mainly semiconductors, to high values during short periods (minutes or even less). As such, it can be used as a multi-functional and versatile microfabrication tool, capable of performing rapid thermal oxidation, hydrogenation, annealing and nitridation, among others. The project focused on the first three, which led to several experimental studies. According to the results, the atom migration phenomenon was witnessed in both 5% hydrogen/argon-ambient and argon-ambient rapid thermal annealing (RTA). Thus, it resulted in either three-dimensional (3D) profile transformation or silicon-on-nothing (SON) structures due to empty-space-in-silicon (ESS) formation. However, silicon volume loss was reported, possibly caused by sublimation and etching by reaction with oxygen (O2). Furthermore, the tool was able to grow uniform silicon oxide (SiO2) thin films –below 17 nm and 20 nm for Si (100) and Si (110) surfaces, respectively. The removal of previously grown black silicon (BSi) was also accomplished by RTA, with some margin for improvement. In general, a better understanding of these techniques will allow for their insertion, for instance, into the metal-oxide-semiconductor (MOS) and micro-electromechanical systems (MEMS) devices manufacturing process and the large scale integrated circuits world.