Enlargement of step-free SiC surfaces by homoepitaxial web growth of thin SiC cantilevers

Abstract

Lateral homoepitaxial growth of thin cantilevers emanating from mesa patterns that were reactive ion etched into on-axis commercial SiC substrates prior to growth is reported. The thin cantilevers form after pure stepflow growth removes almost all atomic steps from the top surface of a mesa, after which additional adatoms collected by the large step-free surface migrate to the mesa sidewall where they rapidly incorporate into the crystal near the top of the mesa sidewall. The lateral propagation of the step-free cantilevered surface is significantly affected by pregrowth mesa shape and orientation, with the highest lateral expansion rates observed at the inside concave corners of V-shaped pregrowth mesas with arms lengthwise oriented along the ͗1100͘ direction. Complete spanning of the interiors of V's and other mesa shapes with concave corners by webbed cantilevers was accomplished. Optical microscopy, synchrotron white beam x-ray topography and atomic force microscopy analysis of webbed regions formed over a micropipe and closed-core screw dislocations show that c-axis propagation of these defects is terminated by the webbing. Despite the nonoptimized process employed in this initial study, webbed surfaces as large as 1.4ϫ10 Ϫ3 cm 2 , more than four times the pregrowth mesa area, were grown. However, the largest webbed surfaces were not completely free of bilayer steps, due to unintentional growth of 3C-SiC that occurred in the nonoptimized process. Further process optimization should enable larger step-free webs to be realized.

On-axis homoepitaxial growth on Si-face 4H–SiC substrates

“…As the layer was intentionally doped, the intensity of N-BE is higher than the FE peak. For low-doped material with nitrogen concentration lower than 3×10 16 cm −3 , the relative intensity between the N-BE no-phonon line, such as Q 0 in 4H-SiC and one of the FE lines, such as I 76 the strongest phonon replica of the FE, has allowed a quantitative estimation of the doping concentration [26]. The concentration of the nitrogen for this doped layer determined by PL is 3×10 15 cm −3 .…”

“…There have been several reports on epitaxial growth on nominally on-axis 4H and 6H-SiC substrates [15][16][17][18]. Among those only one with successful homoepitaxy; however, the work was conducted on C-face substrates [19].…”

Advanced Electrical Materials and Component Development

“…The present "web growth" process is not considered to be optimized but webbed surfaces as large as 4X10 -3 cm 2 have been grown. This area represents more than 4X the pre-growth mesa area [22].…”

“…To overcome this deficiency in the growth process, the research team has developed a SiC homeopitaxial lateral "web growth" process [21]. Experimental analysis of the webbed regions formed over a micropipe and closed-core screw dislocations show that c-axis propagation of these defects is terminated by the "web growth" process [22]. The present "web growth" process is not considered to be optimized but webbed surfaces as large as 4X10 -3 cm 2 have been grown.…”

Advanced Electrical Materials and Components Development---An Update

“…On commercial 4H-SiC wafers, step free mesas with dimensions up to 200 µm square have been demonstrated while on a 6H-SiC wafer, step free mesas with dimensions up to 50 µm have been produced (ref. 36). This new homoeptaxial growth process is performed on the mesas under conditions that promote step-flow growth and at the same time suppress 2D nucleation on the mesa top.…”