HZO-based FerroNEMS MAC for In-Memory Computing
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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 μm × 30 μm unimorph cantilever with 20 nm thick ferroelectric HZO on 1 μm 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 (δ_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 (δ_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.
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