  Microresonator frequency combs, or microcombs, have gained wide appeal for
their rich nonlinear physics and wide range of applications. Stoichiometric
silicon nitride films grown via low-pressure chemical vapor deposition (LPCVD),
in particular, are widely used in chip-integrated Kerr microcombs. Critical to
such devices is the ability to control the microresonator dispersion, which has
contributions from both material refractive index dispersion and geometric
confinement. Here, we show that modifications to the LPCVD growth conditions,
specifically the ratio of the gaseous precursors, has a significant impact on
material dispersion and hence the overall microresonator dispersion. In
contrast to the many efforts focused on comparison between Si-rich films and
stoichiometric (Si$_3$N$_4$) films, here we entirely focus on films that are
within the nominally stoichiometric growth regime. We further show that
microresonator geometric dispersion can be tuned to compensate for changes in
the material dispersion.
