Nodular defect growth is a problem in evaporated, sputtered, chemical
vapor deposited (CVD), and electrodeposited films. In this work, the f
ormation and structure of nodular defects in evaporated MgF2 and sputt
ered Ti were studied and modeled. A structurally similar but fundament
ally different runaway growth structure was observed in plasma enhance
d CVD (PECVD) Si on Ni. Nodule formation was initiated by seeding the
substrate with polystyrene spheres for both the evaporated and sputter
ed deposits. These nodules grew in a characteristic cone shape with a
domed top, and with the nodule separated from the bulk of the film by
a low density boundary. Simulation of nodule growth using the SIMBAD M
onte Carlo deposition model reproduces the nodular shape as well as th
e low density region which extends from the seed to the film boundary.
Sputtering pressures were found to have little influence on the nodul
e characteristics, although film thickness and surface diffusion can h
ave important effects. Evidence was found to indicate that the defect
structure in the CVD films is due to Ni diffusion into the growing Si
film. The structure differs from the physical vapor deposition nodule
in two respects: extent of the growth and the adhesion of the defect t
o the film.