Calculation of apparent activation energy for the deposition of TEOS-SiO2 films by PECVD

Apparent activation energy for the deposition of SiO2 films from tetraethyl orthosilicate(TEOS)/O-2 discharges is calculated using the electron-induced dissociation model which describes the radical concentration in the steady state of a uniform plasma. The model is modified for a isobaric plasma to give the deposition rate of TEOS-SiO2 films as a function of the gas temper ature adjacent to the substrate. In the scheme where organo-silane film pre cursors formed from TEOS completely cover the surface and thus the oxygen r adical flux to the surface of growing films is the rate-limiting step, the model predicts that the apparent activation energies lie well in the range of -k(B)T(s) to -2k(B)T(s) (with k(B) the Boltzmann's constant and T-s the surface temperature, respectively), dependent on the discharge power, press ure, and the flow rate of reaction gases. The values of activation energy a t T-s of 700 and 300 K are calculated to be -2.78 and -0.60 kcal/mol, respe ctively, which are consistent with those of estimated experimentally by oth er researchers. The model is further modified to attain a generalized form and on that basis the origin of the negative and temperature-dependent acti vation energy is discussed. (C) 1999 Elsevier Science S.A. All rights reser ved.