  The reference design for the next-generation cosmic microwave background
(CMB) experiment, CMB-S4, relies on large arrays of transition edge sensor
(TES) bolometers coupled to Superconducting Quantum Interference Device
(SQUID)-based readout systems. Mapping the CMB to near cosmic variance limits
will enable the search for signatures of inflation and constrain dark energy
and neutrino physics. AlMn TESes provide simple film manufacturing and highly
uniform arrays over large areas to meet the requirements of the CMB-S4
experiment. TES parameters such as critical temperature and normal resistance
must be tuned to experiment specifications and can be varied based on geometry
and steps in the fabrication process such as deposition layering, geometry, and
baking time and temperature. Using four-terminal sensing, we measured $T_C$ and
$R_N$ of AlMn 2000 ppm films and devices of varying thicknesses fabricated at
Argonne National Laboratory to motivate device geometries and fabrication
processes to tune $T_C$ to 150-200 mK and $R_N$ to $\sim$10 mOhms. Measurements
of IV curves and time constants for the resulting devices of varying leg length
were made using time-division SQUID multiplexing, and determined $T_C$, $G$,
$k$, $f_{3db}$, and $R_N$. We present the results of these tests along with the
geometries and fabrication steps used to tune the device parameters to the
desired limits.
