Atomically controlled CVD processing of group IV semiconductors for ultra-large-scale integrations

One of the main requirements for ultra-large-scale integrations (ULSIs) is atomic-order control of process technology. Our concept of atomically controlled processing is based on atomic-order surface reaction control by CVD. By ultraclean low-pressure CVD using SiH4 and GeH4 gases, high-quality low-temperature epitaxial growth of Si_1-xGe_x (100) (x = 0-1) with atomically flat surfaces and interfaces on Si(100) is achieved. Self limiting formation of 1-3 atomic layers of group IV or related atoms in the thermal adsorption and reaction of hydride gases on Si_1-xGe _x (100) are generalized based on the Langmuir-type model. By the Si epitaxial growth on top of the material already-formed on Si(100), N, B and C atoms are confined within about a 1 nm thick layer. In Si cap layer growth on the P atomic layer formed on Si_1-xGe_x (100), segregation of P atoms is suppressed by using Si2H6 instead of SiH4 at a low temperature of 450.C. Heavy C atomic-layer doping suppresses strain relaxation as well as intermixing between Si and Ge at the Si_1-xGe_x/Si heterointerface. It is confirmed that higher carrier concentration and higher carrier mobility are achieved by atomic-layer doping. These results open the way to atomically controlled technology for ULSIs.