STRAIN-MEASUREMENTS IN THIN-FILM STRUCTURES BY CONVERGENT-BEAM ELECTRON-DIFFRACTION

The Convergent Beam Electron Diffraction technique (CBED) has been app lied to determine the lattice strain in Si1-xGex/Si heterostructures a nd below patterned films on silicon substrates. The well known problem of the stress relaxation which occurs in thinned TEM samples has been overcome, in the case of the heterostructures, by applying the isotro pic elasticity theory to the lattice constants measured along differen t crystallographic directions through the shift of the High Order Laue Zone (HOLZ) lines in the central disk of the CBED patterns. In this w ay bulk strain values. have been obtained, in good agreement with valu es deduced from independent techniques. In patterned structures, the h igh spatial resolution of the CBED technique has been applied to deter mine the distribution of the components of the strain tensor induced i nto oxidized silicon substrates by Si3N4 stripes. A good agreement wit h the results obtained using numerical computations has been found.