Silicon Tetrafluoride dopant gas for silicon ion implantation

摘要

Silicon Tetrafluoride (SiF) is a dopant gas of choice for different silicon ion implantation processes used in semiconductor device engineering. It is a primary source of atomic dopants like Si and F, and a potential source of molecular dopants (e.g. Si, SiF, x=1–3). A significant challenge associated with the use of SiF is that it can compromise ion source performance, resulting in poor beam stability and source life. This is primarily the result of the formation of a halogen cycle that takes place due to the presence of fluorine from the SiF molecule along with tungsten materials that are present in the ion source (e.g. liners, walls). A second challenge associated with SiF can be limited beam current. In order to improve implant tool performance when using SiF, the following investigations have been performed: (1) Characterization of SiF / H mixtures: The addition of hydrogen co-gas can effectively mitigate the halogen cycle and improve source performance. Using the magnitude of the resulting WF peaks as an indicator, the degree to which the halogen cycle is mitigated is shown as a function of H flow rate. Also, in that single packages may impart various advantages, SiF / H co-mixture stability data are provided. (2) Characterization of enriched (en) SiF: The additional enrichment can enable higher beam currents of Si. The effect of En-SiF flow rate on beam current is presented, along with the resulting WF spectra. (3) Initial observations of SiF beams are provided, along with the potential benefits that may be obtained in selecting this molecular ion.