Vertically Aligned SiNW Arrays with TCS as Precursor
Mathieu R. Monville1, Shihsheng Chang1, Samuel Wright1, Karlheinz Strobl1
CVD Equipment Corporation, 355 S. Technology Drive, Central Islip, New York 11722, USA
Silicon nanowires (SiNWs) attract growing interest due to their high multi-functional potential, spanning from energy harvesting and storage, thermoelectricity, and protein detection to gas sensing applications.
A narrow distribution in properties (length, diameter, doping levels) and microscopic arrangement are sought-after for most applications for which reducing materials production costs is often a necessary condition for development. Specific arrangement of silicon nanowires vertically or even horizontally (respectively VASiNW and HASiNW) is also desirable to efficiently integrate silicon nanowires into nano-enabled devices.
Chemical vapor deposition (CVD) and room temperature metal assisted chemical etching are the most commonly used fabrication techniques. So far the conventional route of Vapor-Liquid-Solid (VLS) growth by CVD has utilized two silicon precursors: silane (SiH4) and silicon tetrachloride (SiCl4) which are commonly used in high quality semiconductor manufacturing and are available at high purity levels. These two precursors are also not the-containing precursors of the lowest cost. Silane is a preferred precursor for high purity processing at relatively low temperatures (500 - 600 °C), but the resulting nanowires are typically randomly aligned. By adding hydrogen chloride (HCl) to the process, and choosing a silicon (111) wafer as the growth surface, epitaxial growth of nanowires can be achieved. For the case of SiCl4, additional HCl is not required since HCl is generated as a byproduct of the reaction in a hydrogen-containing atmosphere. However the downside is the even higher cost of silicon tetrachloride and higher process temperature requirements limiting large scale processing of VASiNW.
Here we present our investigations on the use of the Si precursor of lowest cost and highest volume production, i.e. trichlorosilane (TCS), to develop VLS-CVD of vertically aligned arrays of high quality silicon nanowires at atmospheric pressure with growth rates of around 5µm/min. Our results show good uniformity in height (a few tens of micrometers) and diameter (a few tens of nanometers), thereby paving the way for cost-effective synthesis of large volumes of crystalline, highly oriented SiNW arrays.
Submitted to MRS Fall 2014 Meeting in Boston, MA