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Silicon dioxide is used to electrically isolate CMOS devices such as fin field effect transistors by filling gaps between the devices (also known as shallow trench isolation). The gap fill oxide typically requires a high temperature anneal in excess of 1000 °C to achieve adequate electrical properties and oxide densification to make the oxide compatible with subsequent fabrication steps such as fin reveal etch. However, the transition from Si-based devices to high mobility channel materials such as SiGe and III-V semiconductors imposes more severe thermal limitations on the processes used for device fabrication, including gap fill oxide annealing. This study provides a framework to quantify and model the effect of anneal temperature and time on the densification of a flowable silicon dioxide as measured by wet etch rate. The experimental wet etch rates allowed the determination of the activation energy and anneal time dependence for oxide densification. Dopant and self-diffusion can degrade the channel material above a critical temperature. We present a model of self-diffusion of Ge and Si in SiGe materials. Together these data allowed us to map the thermal process space for acceptable oxide wet etch rate and self-diffusion. The methodology is also applicable to III-V devices, which require even lower thermal budget. The results highlight the need for nonthermal oxide densification methods such as ultraviolet (UV) and plasma treatments. We demonstrate that several plasma treatments, in place of high temperature annealing, improved the properties of flowable oxide. In addition, UV curing prior to thermal annealing enables acceptable densification with dramatically reduced anneal temperature. [ABSTRACT FROM AUTHOR]

We conducted isochronal stress hysteresis measurements coupled with thermal desorption spectroscopy on silicon nitride thin films obtained by performing plasma enhanced chemical vapor deposition on (001) silicon wafers. Above the deposition temperature, we observed irreversible stress build-up in parallel to substantial hydrogen effusion out of the films. We confirmed that the hydrogen dissociation and stress build-up can be modeled with similar kinetic equations. The hydrogen dissociation and stress development activation energies as well as the hydrogen diffusion coefficients were determined by fitting the experimental data with solutions to the kinetics and Fickian diffusion equations obtained with the finite difference method. A first order correlation was found between the hydrogen diffusion coefficients calculated between 400 and 800 °C and the silicon nitride film density. [ABSTRACT FROM AUTHOR]