Stresses in SiO₂ Films Obtained from the Thermal Decomposition of Tetraethylorthosilicate—Effect of Heat‐Treatment and Humidity

The interference fringe method was used for measurement of stresses in films deposited on Si and Ge substrates. An attempt has been made to deduce both the amount of stress resulting from intrinsic stress and the stress arising from mismatch of temperature coefficient of expansion. From measurement at room temperature of stress in films deposited by thermal decomposition of tetraethylorthosilicate at 725°C in forming gas , or at 450°C in oxygen , it is concluded that the intrinsic stress is tensile. The mechanical properties of the films prepared by these two methods were assumed to be similar to those of bulk vitreous silica. An explanation is offered for the observed increase in the room temperature tensile stress of the film on heat‐treatment to 700°C, and to the following decrease in tensile stress on heat‐treatment to 800°C. A decrease in the room temperature stress in the film occurs on exposure of the film to a humid ambient.