Study of Selective Graphene Growth on a SiO2-Patterned Ge/Si(001) Substrate
To adapt graphene layer into CMOS process, various growth techniques are needed such as direct and selective growth at low temperature. The selective growth on heterogeneous substrate is the key technology to make various structures including graphene realistic. In this study, we addressed the origin of selective growth of nano-crystalline graphene (nc-G) on semiconductor over on dielectric materials. First of all, we found that the adsorption energy of CH4 on SiO2 is much higher than that on Si and Ge from Ab initio simulation. Difference of nc-G growth on Ge and SiO2 was also experimentally confirmed. While a continuous nc-G layer was formed on the Ge surface at the initial growth stage and became thicker by increasing growth time, an incubation time is required for nc-G to be nucleated on SiO2. The analysis of interface between nc-G and SiO2 indicates that initially incorporated carbons cannot contribute to the nc-G growth because they reduce SiO2 by forming CO as a by-product. Finally, 3.0 nm-thick nc-G layer were selectively grown on a SiO2-patterned Ge/Si(001) substrate. The selective graphene growth on a patterned semiconductor substrate will help to widen its applications in CMOS.