Piezoelectric Response of Polycrystalline Silicon‐Doped Hafnium Oxide Thin Films Determined by Rapid Temperature Cycles

Abstract

The in‐plane piezoelectric response of 20 nm thick Si‐doped HfO2 is examined by exploiting thermal expansion of the substrate upon rapid temperature cycling. The sample is heated locally by a deposited metal film, and the subsequently registered pyroelectric current is found to be frequency dependent in the observed range of 5 Hz to 35 kHz. While the intrinsic response remains constant, the secondary contribution can be switched off in the high‐frequency limit due to substrate clamping. As this secondary response is generated by thermal expansion and the piezoelectric effect, this allows for extraction of the corresponding in‐plane response. By comparing pyroelectric measurements in low‐ and high‐frequency limits, a piezoelectric coefficient d31 of −11.5 pm V −1 is obtained, which is more than five times larger than that of AlN. The magnitude of piezoelectric response increases upon electric field cycling, which is associated with a transition from antiferroelectric‐like behavior to a purely ferroelectric polarization hysteresis. The hafnium oxide material system is proposed as a promising candidate for future CMOS compatible piezoelectric micro‐ and nano‐electromechanical systems (MEMS and NEMS).

On the Origin of Wake‐Up and Antiferroelectric‐Like Behavior in Ferroelectric Hafnium Oxide

“…Since its discovery, [1] ferroelectric hafnium oxide has become of interest for a broad range of integrated devices, such as ferroelectric field effect transistors (FeFETs), ferroelectric random access memory (FeRAM), and ferroelectric tunnel junctions (FTJs), [2][3][4][5] as well as piezo-and pyroelectric devices, [6,7] due to its compatibility to standard complementary metal-oxide-semiconductor (CMOS) processes. [8] Ferroelectric HfO 2 has enabled highly scalable devices in 28, [9] 22, [10] and 14 nm [11] technology due to its coercive field, layer thickness scalability, and other advantages as compared to conventional ferroelectrics such as lead titanate zirconate (PZT).…”

Influence of Annealing Temperature on the Structural and Electrical Properties of Si-Doped Ferroelectric Hafnium Oxide

“…The discovery of ferroelectricity in the hafnium oxide material system enabled a large variety of device applications, ranging from nonvolatile memories , and neuromorphic devices − to pyroelectric sensors and piezoelectric actuators. − However, recent studies have highlighted the importance of the grain composition on the device performance, − e.g., due to the presence of percolation paths in ferroelectric field-effect transistors . Therefore, microstructure engineering is of major importance to further improve the device performance.…”

Substrate-dependent differences in ferroelectric behavior and phase diagram of Si-doped hafnium oxide

“…The possibility for nand p-type FeFETs [5] enables in addition a larger freedom for novel circuit designs. Moreover, this material system has spurred attention in other applications, like neuromorphic devices [6][7][8], energy harvesting [9,10], sensors and actuators [11,12].…”