  A silicon 3D detector with a single cell of 50x50 um2 was produced and
evaluated for timing applications. The measurements of time resolution were
performed for 90Sr electrons with dedicated electronics used also for
determining time resolution of Low Gain Avalanche Detectors (LGADs). The
measurements were compared to those with LGADs and also simulations. The
studies showed that the dominant contribution to the timing resolution comes
from the time walk originating from different induced current shapes for hits
over the cell area. This contribution decreases with higher bias voltages,
lower temperatures and smaller cell sizes. It is around 30 ps for a 3D detector
of 50x50 um2 cell at 150 V and -20C, which is comparable to the time walk due
to Landau fluctuations in LGADs. It even improves for inclined tracks and
larger pads composed of multiple cells. A good agreement between measurements
and simulations was obtained, thus validating the simulation results.
