Stress-relief behavior in chemical-vapor-deposited diamond films

Biaxial stress in diamond film deposited on titanium coated copper substrate is investigated. Raman spectra show that with an increase in the film thickness, the diamond Raman line shifts from higher wave numbers to lower, approaching 1332 cm(-1). Fitting the experimental plot of the in-plane stress sigma(x) versus the film thickness y yields a linear function sigma(x)=(0.186y-5.776) GPa. On the other hand, the biaxial stress is modeled from Airy stress theory, showing also that the stress changes linearly along the film-growth direction. A critical him thickness h(c)=31 mu m is found at which the compressive stress is completely released. In addition, it is shown that the variation of the biaxial stress is less than 5% (similar to 0.28 GPa) throughout the thickness of a film thinner than 1.5 mu m. Therefore, the stress in such a thin diamond film can be considered uniform according to the Raman measurement due to the spectrum resolution. (C) 1998 American Institute of Physics.