Tim P. LaFave Jr. | Fabrication and modeling of rapid, low temperature silcon-on-insulator using solid-medal-mediated epitaxy on Si(100) and Si(111).

A new silicon on insulator (SOI) fabrication technology, solid-metal-mediated epitaxy (SMME), is investigated. SMM-SOI offers a low temperature alternative to current industrial methods. A crystal aluminum (Al) film is deposited atop Si(100) and Si(111) wafers at room temperature. The substrate is heated to 300 - 500°C. Silicon (Si) is deposited on the Al film and observed to diffuse through the Al film and grow at the buried Si/Al interface as single-crystal Si. On oxide patterned wafers, the buried Si film grows as a single crystal in seed areas (spaces between oxide regions) and subsequently grows laterally over the oxide regions. In situ reflective high energy electron diffraction (RHEED) is used to monitor the growth of thin films during deposition in ultra high vacuum (UHV). Crystalline epitaxial lateral overgrowth of silicon is observed by use of selected area transmission electron diffraction (TED). Scanning electron microscopy (SEM) is combined with optical microscopy investigations of the resulting surface to examine the overall process. A basic growth model for both the Al and Si film is proposed and used as the basis of explaining observed phenomena. This process can be performed in existing industrial equipment, and is therefore a cost-effective solution to today's SOI fabrication needs. SMM-SOI is primarily targeted as a local SOI fabrication technology that is ideal for three-dimensional device structures that require a low thermal budget. Here, due to the nature of the investigated mediator-diffusor pair of Al-Si, only p-type films have been grown. Combined with an n-type SOI fabrication method, complete devices may be fabricated.