INTRINSIC STRESS IN HYDROGENATED AMORPHOUS-CARBON PREPARED BY RF PLASMA DECOMPOSITION OF METHANE

An unconventional analytical/empirical approach was used to determine the intrinsic stress in thin films of hydrogenated amorphous carbon (a-C:H) from measurements at room temperature of total stress on glass. The a-C:H was deposited through the decomposition of methane in an rf plasma over a range of conditions defined by two parameters; namely, the self-bias voltage on the substrate support electrode, V(b), and the pressure of methane in the deposition chamber, P. The intrinsic stress was found to differ from the total stress at room temperature by a thermal stress introduced by the deposition process. Over the range of deposition conditions investigated, 400 less-than-or-equal-to V(b) less-than-or-equal-to 1600 V and 1 less-than-or-equal-to P less-than-or-equal-to 16 mTorr, the intrinsic stress was compressive, high in level (varying only slightly between 1-3 x 10(10) dynes/cm2) and proportional to a function of the deposition parameters, V(b)-1/4P1/8. Over the same range of conditions, the thermal stress (at approximately 20-degrees-C) was tensile and proportional to V(b)3/2P1/4. At the highest values of V(b) and P investigated, 1600 V and 16 mTorr, respectively, the level of the thermal stress (approximately 0.8 x 10(10) dynes/cm2) exceeded the level of the total stress (approximately 0.3 x 10(10) dynes/cm2) by a significant margin. Implications are discussed.