Polycrystalline inclusion-free growth of thick, lattice-matched SiGeC with high substitutional Carbon concentrations up to 2

State of the art semiconductor manufacturing seeks to expand its range of Si-based materials with novel properties, boosting performance to comply with customer demands. These materials mostly comprise of large lattice parameter materials like Ge-rich or group III/V alloys. To reduce costs, heteroepitaxy of these materials on Si substrates is desired. Buffer solutions like SiGe [1] or Ge Virtual Substrates [2] or III/V patterned Superlattices [3] usually do not result in threading dislocations densities below 10 6 cm -2 , which affects device performance and process robustness. The incorporation of Carbon into SiGe allows to tailor SiGe’s lattice parameter, theoretically enabling to match the Si substrate’s lattice parameter. This allows the strain-free growth of a few hundred nanometers up to several micrometers thick SiGeC on a Si substrate without the formation of dislocations. The growth of SiGeC was performed in a 300 mm industrial standard Reduced Pressure-Chemical Vapor Deposition (RP-CVD) reactor. Si 2 H 6 , GeH 4 and SiH 3 CH 3 were used as precursors with constant flows at 550°C, 10 Torr. Interstitial ( C Int ) and substitutional Carbon ( C Sub ) concentrations were determined by XPS. [4] For a 50 nm SiGeC layer with C Int ~0.4% and C Sub =2.0%, smooth surfaces were observed by top view Scanning Electron Microscopy (SEM) ( Fig. 1 (a) ) and confirmed by Atomic Force Microscopy (AFM) ( Fig. 1 (b) ) with a RMS of 0.23 nm. X-Ray Diffraction measurements showed the growth of SiGeC lattice matched to the Si substrate ( Fig. 1 (c) ). Above ~250 nm, islands are visible on the surface by top-view SEM ( Fig. 2 (a) ) with the island’s diameter increasing as the SiGeC layer thickness increased. Transmission Electron Microscopy showed a dislocation free growth and that the islands/clusters were polycrystalline, originating from several hundred nanometers below the surface ( Fig. 2 (b) ). Growing SiGeC of the same thickness range under the same growth conditions with lower SiH 3 CH 3 flow, resulted in fully substitutional incorporated Carbon with C Sub ~1.0% and C Int below the detection limit. No islands/clusters were observed by SEM and AFM ( Fig. 2 (c) ). The elimination of C Int allowed to suppress the formation of polycrystalline SiGeC inclusions. The starting point of these defects should be due to point defects formed by C int clusters. Even if the reduction of SiH 3 CH 3 flow resulted in defect free growth of thick SiGeC on Si substrates, other approac