  This paper demonstrates a hafnium zirconium oxide (HZO)-based ferroelectric
NEMS unimorph as the fundamental building block for very low-energy capacitive
readout in-memory computing. The reported device consists of a 250 $\mu$m
$\times$ 30 $\mu$m unimorph cantilever with 20 nm thick ferroelectric HZO on 1
$\mu$m $SiO_2$.Partial ferroelectric switching in HZO achieves analog
programmable control of the piezoelectric coefficient ($d_{31}$) which serves
as the computational weight for multiply-accumulate (MAC) operations. The
displacement of the piezoelectric unimorph was recorded by actuating the device
with different input voltages $V_{in}$. The resulting displacement was measured
as a function of the ferroelectric programming/poling voltage $V_p$. The slopes
of central beam displacement ($\delta_{max}$) vs $V_{in}$ were measured to be
between 182.9nm/V (for -8 $V_p$) and -90.5nm/V (for 8 $V_p$), demonstrating
that $V_p$ can be used to change the direction of motion of the beam. The
resultant ($\delta_{max}$) from AC actuation is in the range of -18 to 36 nm
and is a scaled product of the input voltage and programmed $d_{31}$ (governed
by the $V_p$). The multiplication function serves as the fundamental unit for
MAC operations with the ferroelectric NEMS unimorph. The displacement from many
such beams can be added by summing the capacitance changes, providing a pathway
to implement a multi-input and multi-weight neuron. A scaling and fabrication
analysis suggests that this device can be CMOS compatible, achieving high
in-memory computational throughput.
