| AVS 61st International Symposium & Exhibition | |
| Selective Deposition as an Enabler of Self-Alignment Focus Topic | Wednesday Sessions |
| Session SD-WeM |
| Session: | Fundamentals of Selective Deposition |
| Presenter: | Mary Edmonds, University of California, San Diego |
| Authors: | M. Edmonds, University of California, San Diego T. Kent, University of California, San Diego R. Droopad, Texas State University E.A. Chagarov, University of California, San Diego A.C. Kummel, University of California, San Diego |
| Correspondent: | Click to Email |
A broader range of channel materials allowing better carrier confinement and mobility could be employed if a universal control monolayer (UCM) could be ALD or self-limiting CVD deposited on multiple materials and crystallographic faces. Si-OH is a leading candidate for use as the UCM, as silicon uniquely bonds strongly to all crystallographic faces of InGa1-xAs, InxGa1-xSb, InxGa1-xN, SiGe, and Ge enabling transfer of substrate dangling bonds to silicon, which is then passivated by atomic hydrogen. The surface may subsequently be functionalized with an oxidant such as HOOH(g) in order to create the UCM terminating Si-OH layer. This study focuses on depositing a saturated Si-H seed layer via two separate self-limiting and saturating CVD processes on InGaAs(001)-(2x4) at substrate temperatures of 250°C and 400°C. XPS in combination with STS/STM were employed to characterize the electrical and surface properties of the saturated silicon seed layers on InGaAs(001)-(2x4).
The 250°C self-limiting CVD procedure includes a decapped In0.53Ga0.47As(001)-(2x4) surface dosed with 300 MegaLangmuir of Si3H8 at sample temperature of 250°C. The 400°C self-limiting CVD procedure includes a decapped surface dosed with 21 MegaLangmuir of Si2Cl6, followed by a 500 Langmuir dose of atomic hydrogen at sample temperature of 400°C, leaving the silicon surface hydrogen terminated. The XPS spectra following the saturated Si3H8 and Si2Cl6 doses shows the increase of the silicon 2p3/2 peak and decrease in the gallium 3p3/2 substrate peak, indicative of saturating coverage. Complete saturation is determined to occur once further dosing with Si3H8 or Si2Cl6 leads to no further increase in the silicon 2p peak or further decrease in the gallium 3p peak areas. STM images of the decapped surface following Si3H8 CVD at 250°C and post annealing shows high surface order. STM images of the saturated Si2Cl6 surface followed by 500 Langmuir atomic hydrogen at 400°C show silicon absorbs in a commensurate structure with average row spacing nearly identical to the (2x4) surface at 1.5 nm, consistent with III-V dangling bond elimination. Both CVD processes employ high pressure CVD pulses, which protect from unwanted carbon and oxygen contamination. The hydrogen terminated silicon surface achieved by both CVD procedures show identical STS results with the surface Fermi level remaining at the same location as the n-type clean (2x4) surface and conduction and valance band edges lining up, indicating both processes do not pin the Fermi level nor degrade the surface density of states.