Atomically controlled processing in silicon-based CVD epitaxial growth

One of the main requirements for Si-based ultrasmall device is atomic-order control of process technology. Here, we show the concept of atomically controlled processing for group IV semiconductors based on atomic-order surface reaction control in Si-based CVD epitaxial growth. Self-limiting formation of 1-3 atomic layers of group IV or related atoms after thermal adsorption and reaction of hydride gases on Si_1-xGe_x(100) (x = 0-1) surface are generalized based on the Langmuir-type model. Moreover, Si-based epitaxial growth on N, P or C atomic layer formed on Si_1-xGe _x100 surface is achieved at temperatures below 500 °C. N atoms of about 4×10¹⁴ cm^-2 are buried in the Si epitaxial layer within about 1 nm thick region. In the Si_0.5Ge_0.5 epitaxial layer, N atoms of about 6×10¹⁴ cm^-2 are confined within about 1.5 nm thick region. The confined N atoms in Si _1-xGe_x preferentially form Si-N bonds. For unstrained Si cap layer grown on top of the P atomic layer formed on Si_1-xGe _x100with P atomic amount of below about 4×10¹⁴ cm^-2 using Si₂H₆ instead of SiH₄, the incorporated P atoms are almost confined within 1 nm around the heterointerface. It is found that tensile-strain in the Si cap layer growth enhances P surface segregation and reduces the incorporated P atomic amount around the heterointerface. Heavy C atomic-layer doping suppresses strain relaxation as well as intermixing between Si and Ge at the nm-order thick Si_1-xGe_x /Si heterointerface. These results open the way to atomically controlled technology for ULSIs.