טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentZaid Tal
SubjectElectrochemistry of Silicon at High Anodic Potentials
DepartmentDepartment of Materials Science and Engineering
Supervisor Professor Yair Ein-Eli
Full Thesis textFull thesis text - English Version


Abstract

The development of both fast and cost effective processes for single and multi-crystalline silicon texturing is of great interest in the microelectronics and the solar cells industries. Wet electrochemical etching is known as an efficient and rapid dissolution because of the ability to accurately control the process through experimental conditions.  A rather simple electrochemical process for silicon dissolution is discussed. Such a method is accomplished by applying typically passivating positive (anodic) potentials in conditions of wet etching in HF-free solutions containing alkaline (KOH). The application of anodic biasing results in the fastest ever reported etching, with silicon removal rate values of more than 30 um/min for single crystal, and more than 20 um/min for poly-silicon. Scanning Electron Microscopy indicate that due to exposure to extremely high anodic biasing on a single crystal silicon, a variety of textures can be formed, from porous to polished surfaces. For multi-crystalline silicon, surface texturing evolved from the unexpected isotropic texture at lower potentials to anisotropic etching at elevated potentials. Light reflection measurements show that up to 40% reduction of reflection can be accomplished for isotropic textured surface.  The combined effects of both extreme high applied potential and high alkaline concentration are primarily responsible for the rapid etching rates observed, as well as the modifications in surface textures.