Process technology development for advanced silicon heterostructure devices

The semiconductor industry is constantly trying to find ways to make faster, less expensive, and more complex integrated circuit (IC) chips. In order to achieve these goals, smaller individual devices, nonplanar device structures, and heterostructure materials are often incorporated into ICs. Due to the challenges of multi-dimensional design and heterostructure integration, many broad technology issues are encountered throughout the fabrication process of these innovative devices. This work examines the diffusion and oxidation processes in silicon and silicon germanium (SiGe)-based heterostructures for advanced device application. A combination of experiments and process modeling has been used to investigate the suppression of boron transient enhanced diffusion (TED) by carbon in Si and SiGe, crystallographic orientation effects upon Si wet oxidation, and two-dimensional (2-D) oxidation of Si and SiGe.; With the continued scaling of heterostructure devices to smaller dimensions, TED is particularly important to understand and control because of the often undesirable dopant redistribution that results from it. In this study, the time-evolved phenomenon of B TED suppression by C in Si and SiGe has been investigated and a comprehensive model of dopant, point defect, and C interactions has been developed to simulate the experimental data. With the advent of nonplanar device configurations and shrinking minimum feature sizes, crystallographic orientation effects upon the oxidation process become increasingly significant. The initial wet oxidation regime of (100), (110), and (111) oriented Si has therefore been examined. The results of this work have demonstrated for the first time that rapid initial oxide growth of Si(110) and an oxidation rate crossover of the (110) and (111) planes occur for wet oxidation. These anomalous phenomena have previously been believed to be confined to dry oxidation. It is known that 2-D effects also have a significant impact upon the oxidation of small, nonplanar structures due to oxidation retardation on curved surfaces caused by stress and nonplanar oxide deformation. In order to investigate such effects, oxides on submicron-sized pillars of Si and SiGe have been grown in wet and dry ambients. The results have been modeled and qualitative and quantitative observations have been made comparing the stress-dependent oxidation of these materials.