AVS 59th Annual International Symposium and Exhibition
    Spectroscopic Ellipsometry Focus Topic Monday Sessions
       Session EL+TF+AS+EM+SS+PS+EN+NM-MoM

Paper EL+TF+AS+EM+SS+PS+EN+NM-MoM9
The Effect of Stress on the Optical Properties Semiconductor Films

Monday, October 29, 2012, 11:00 am, Room 19

Session: Spectroscopic Ellipsometry for Photovoltaics and Semiconductor Manufacturing
Presenter: A.C. Diebold, College of Nanoscale Science and Engineering, University at Albany
Authors: A.C. Diebold, College of Nanoscale Science and Engineering, University at Albany
G.R. Muthinti, College of Nanoscale Science and Engineering, University at Albany
M. Medikonda, College of Nanoscale Science and Engineering, University at Albany
T.N. Adam, College of Nanoscale Science and Engineering, University at Albany
A. Reznicek, IBM Research at Albany Nanotech
B. Doris, IBM Research at Albany Nanotech
Correspondent: Click to Email
Here we review the impact of stress on the complex dielectric function of semiconductor films measured using spectroscopic ellipsometry. Two relevant examples of stressed semiconductor layers are pseudomorphic epitaxial layers fabricated during semiconductor manufacturing and strained silicon on insulator (sSOI) wafers. Stress is known to shift the energies of direct gap critical point transitions in semiconductors. The biaxial stress in pseudomorphic films grown on silicon wafers can be as high as that used during opto-elastic studies of bulk semiconductors. The amount of stress in un-relaxed, pseudomorphic films of Si1-xGex on Si (100) reaches 1 GPa for alloys with 20% Ge and is more than 3 GPa for films with > 50% Ge. The bi-axial stress in sSOI is typically ~1 GPa. An elastic theory approach for the effect of strain on the k*p determined band structure and optical transition energy is well known. Both low shear stress and high shear stress approximations can apply to the shift in transition energy depending on the magnitude of the spin orbit splitting energy vs the magnitude of the shear stress. Until recently it was difficult to obtain sets of samples that test both approximations. Here we discuss results from our recent study of pseudomorphic films of Si1-xGex on Si (100) from x= 0.05 to 0.75 which covers both low and high shear regimes. We also present our recent study of the dielectric function of thinned sSOI which illustrates the impact of stress on the optical transitions for the Si layer on sSOI. All of these samples are examples of new materials being used in semiconductor research. The results of this study are directly transferred into cleanroom spectroscopic ellipsometry systems used for process control during manufacturing.