  We used the Coherent Grazing Incidence Small Angle X-Ray Scattering
(Co-GISAXS) technique to study the average kinetics and nanoscale dynamics
during early-stage a-WSi$_2$ sputter deposition. The kinetic and dynamic
properties are examined as a function of pressure, which is known to be a
critical factor in determining final surface roughness. Surface growth kinetics
and dynamics are characterized by time parameters extracted from the
height-height structure factor and correlation functions. The roughness at a
given length scale reaches a maximum before relaxing down to a steady state.
The lateral length scale dependence and pressure dependence are then compared
among measured kinetics and dynamics time parameters. Surfaces grown at lower
pressures are smoother, leading to longer correlation times. The time to reach
a dynamic steady state and a kinetic steady state show contrasting pressure
dependence. A dynamic steady state is reached earlier than the kinetic steady
state at high pressure. A more random deposition direction and lower kinetic
energy at higher pressures can explain these phenomena, along with the
hypothesis that larger nanoclusters form in vapor before arriving at the
surface. A continuum model is applied to simulate the overall behavior with
mixed success.
