<p>Preparing silicon wafers is a tedious multi-step process that includes etching, polishing, and cleaning. The minimum wafer thickness attainable in current high volume wafer production processes is generally 160 to 300 μm, and the kerf loss for these processes is up to 40% of the total volume. Thin silicon wafers (~30 to 100μm) are very expensive to produce and the wafering process is not cost effective due to the high amount of material loss (more than 80% at these dimensions) during the process and the risk of breakage of the wafers during wafering. In this thesis, a new method called Vapour-Liquid Interface Growth (VLIG) is proposed. VLIG is capable of directly growing a sheet of single crystal silicon without wafering with a thickness of about 30 to 50μm. The features of the process are 1) low temperature operation; 2) the resulting silicon sheet is easily detachable and self-supporting; 3) the resulting sheet has uniform thickness and is single crystal. The system operates in a supersaturated growth solution of an indium-silicon melt. A seed line in a substrate facing down is employed. A layer of single crystal silicon grows on the seed line at the melt surface due to surface segregation during the super cooling process. The grown silicon can grow laterally due to the limited thickness of the melt depth that minimizes growth in the vertical growth direction. The grown silicon can be easily peeled off from the seed line substrate due to the presence of a gap between the grown silicon sheet and the oxide layer on the seed line substrate. The self-supporting silicon sheet now comprises a very thin silicon substrate or sheet.</p> <p>VLIG silicon sheet is characterized by X-ray diffraction to determine the crystallinity. Hall Effect measurements are performed to measure the electrical properties. VLIG silicon sheet is (111) oriented single crystal and it exhibits the same orientation as the substrate. The growth temperature is from 975 to 850<sup>o</sup>C, and the VLIG silicon is p-type doped with indium. The resistivity is 4.181x10<sup>-3</sup> ohm-cm, and the doping level is around 5.3.0x10<sup>18</sup> /cm3. The measured mobility is ranging from 280 cm<sup>2</sup>/V.s. In this study, VLIG demonstrates the potential of growing thin sheet of single crystal silicon with qualities that feasible for photovoltaic application.</p> / Master of Applied Science (MASc)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/12908 |
| Date | 04 1900 |
| Creators | Yu, Hao-Ling |
| Contributors | Kitai, A., Materials Science and Engineering |
| Source Sets | McMaster University |
| Detected Language | English |
| Type | thesis |
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