Silicon needle-like surfaces for room temperature si-si bonding applications

Abstract: This work presents and demonstrates a room temperature silicon-silicon bonding technique using porous silicon-based needle-like surfaces. Silicon (Si) surfaces are functionalized using anodic etching of silicon wafers in a hydrofluoric acid (HF) based electrolyte to create self-organized needle-like surfaces. Such self-organized needlelike surfaces allow repeated bonding and debonding of the same surfaces with
adequate bond strengths at room temperature analogous to Velcro tapes. In the course of this thesis, a simple Si-based technology is described to generate Si needlelike surfaces through anodic etching (anodization) of lowly doped p-type Si wafers in an aqueous HF solution in the transition region (where pore formation and electropolishing compete for control over the surface morphology). Impacts of anodization parameters, wafer resistivity ranges and crystal growth (fabrication) methods, and surface drying methods on morphology of needle-like surfaces are studied and discussed. An optimal process condition to generate such surfaces using 10 - 20 Ωm p-type Si wafers is obtained and presented. In addition, formation mechanisms of needles during anodic etching of 12 - 17 Ωcm p-type Si wafers in a 7.2 wt.% aqueous
HF solution in the transition region is investigated through SEM surface images taken after different etch times. Finally, a simple model based on pore formation models is presented to describe formation of needles during this specific condition. The bonding mechanism between two similar Si needle-like surfaces at room temperature considering deformation and interaction mechanisms of needles is also investigated and mathematically modelled. Deformation mechanism of needles during the bonding is described by the cantilever beam approach, and Van der Waals forces and capillary forces are considered as responsible intermolecular forces in the interaction mechanism of needles. The bond strength between two similar needle-like surfaces due to each intermolecular forces is calculated based on the uncoupled multi-asperity
approach by taking both tip and side interactions of needles into the account. At the end, capability of the bonding technique and validity of the proposed bonding model are demonstrated by comparison with experimental results through four different Si needle-like surfaces with different morphologies

Object Details

• Location: Deutsche Nationalbibliothek Frankfurt am Main
• Extent: Online-Ressource
• Language: Englisch
• Notes: Universität Freiburg, Dissertation, 2019

Classification and Topics

• Classification: Elektrotechnik, Elektronik
• Keyword: Silicon ; Temperature

Contributors, Places and Time

• Event: Veröffentlichung
• (where): Freiburg
• (who): Universität
• (when): 2019
• Creator: Keshavarzi, Shervin
• Contributor: Reinecke, Holger ; Mescheder, Ulrich ; Albert-Ludwigs-Universität Freiburg. Fakultät für Angewandte Wissenschaften

Further information

• DOI: 10.6094/UNIFR/151595
• URN: urn:nbn:de:bsz:25-freidok-1515955
• Rights: Der Zugriff auf das Objekt ist unbeschränkt möglich.
• Last update: 14.08.2025, 10:46 AM CEST