AVS 46th International Symposium
    Surface Science Division Wednesday Sessions
       Session SS1+EM-WeA

Paper SS1+EM-WeA8
Nucleation and Growth of Hemispherical Grained Silicon

Wednesday, October 27, 1999, 4:20 pm, Room 606

Session: Semiconductor Surface Science
Presenter: D. Llera-Rodriguez, University of Illinois, Urbana
Authors: D. Llera-Rodriguez, University of Illinois, Urbana
E.G. Seebauer, University of Illinois, Urbana
Correspondent: Click to Email
Hemispherical grained silicon (HSG) is a material beginning to find widespread use for electrodes in DRAM applications. HSG is formed by the chemical vapor deposition of amorphous Si, followed by a CVD "seeding" step under slightly different growth conditions to form nuclei for surface crystallization. Subsequent rapid thermal annealing to above 600°C induces the nuclei to grow into 100-nm hemispheres via surface diffusion, yielding an electrode with high surface area that increases the capacitance of the resulting device. In addition to the practical applications, however, HSG formation provides useful insights into the fundamental mechanisms of nucleation and growth in a two-dimensional amorphous-to-crystalline phase transition. For example, we can rationalize our experimental results for nucleation density in terms of a rate-equation-based nucleation theory. Furthermore, through a series of growth studies we show that subsequent growth of the initial nuclei can be well-described by a two-dimensional continuum model based on adatom-vacancy pair formation on the amorphous surface, together with diffusion of the atoms toward the growing hemispheres. The activation energy of 2.5 eV describing growth represents the sum of energies for adatom diffusion and surface vacancy formation on the amorphous surface. Somewhat surprisingly, this value for amorphous Si matches that measured by separate experiments for crystalline Si.