Recently developed nanoelectromechanical (NEMS) resonators, which can operate in ultra-high (3-30 GHz) and extremely high (30-300 GHz) frequency ranges, are of great value for the development of more advanced semiconductor electronic products, such as broadband spectrum processors and high-resolution resonant sensors.
recently developed products can be used in ultra-high (3-30 GHz) and extremely high (30-300 GHz) Nanoelectromechanical (NEMS) resonators operating in the frequency range of GHz are of great value for the development of more advanced semiconductor electronic products, such as broadband spectrum processor and high-resolution resonant sensor. The integrated NEMS transducer can realize the development of subminiature sensors and actuators, and realize the atomic level mechanical interaction with the outside world with ultra-high resolution. However, to achieve integrated electromechanical conversion at the nanoscale has proved to be very challenging.
tabrizian, who led the study, said: “our research practices a long-standing pursuit in the field of semiconductor sensors and actuators, that is, truly integrated NEMS transducers. NEMS transducers help to utilize the high-frequency and high-q-value mechanical resonance dynamics in semiconductor nanostructures to achieve monolithic integrated frequency reference and broadband spectrum processors in the centimeter and millimeter wave ranges
in the past decade, researchers have begun to use piezoelectric transducer films to realize MEMS devices for physical sensing and execution applications. Compared with other energy conversion schemes such as optics and magnetism, these thin-film transducers have significant integration advantages. For example, they enable chip level mechanical components, which are critical for many practical applications of MEMS devices, including frequency reference generation, spectrum processing and high-resolution sensing.
tabrizian explains, “however, a major problem with conventional transducer films is their basic scaling limitations. For example, the thickness of aluminum nitride (AlN) films, which are widely used in radio frequency (RF) filters used in smart phones, need to be in the range of hundreds of nanometers to obtain the crystal structure required for effective electromechanical conversion. Further reduction of the film thickness will greatly reduce the electromechanical conversion efficiency, making it impossible for the transducer to detect or sense nano scale micro motion
zirconium hafnium oxide based thin films developed by tabrizian and his colleagues have obvious advantages over traditional transducer films. For example, they can be engineered at the atomic level to achieve efficient electromechanical conversion at a few nanometers thick.
the ultrathin NEMS transducer made of zirconium hafnium oxide (TEM) highlights a 10 nm thick ferroelectric hf0.5zr0.5o2 film sandwiched between 10 nm thick titanium nitride (TIN) electrodes.
this important feature is derived from the unique characteristics of atomic layer hafnium oxide (hafnia), which is used to make metastable crystalline films with ferroelectric properties. When the films are scaled to several nanometers, atomic engineering techniques (such as doping and stacking) can be used to stabilize the metastable phase.
tabrizian said: “hafnium oxide based thin films designed by atomic engineering have recently emerged as a new type of ferroelectric material with great potential for ultra-low power consumption and ultra-small nonvolatile memory cells. In this study, we first used the electrostrictive effect observed by ultrathin ferroelectric zirconium hafnium oxide to realize high frequency and high Q-value NEMS resonators
in their research, the researchers integrated their ultra-thin NEMS transducers into silicon nitride and aluminum nitride thin films to achieve resonators in the frequency range of 340 kHz to 13 GHz, and achieved a record high frequency Q value of 3.97 x 10.
this ultra-thin integrated NEMS transducer, manufactured by tabrizian and his colleagues, opens up new possibilities for the development of new devices for precision sensing, frequency reference generation, spectroscopy and wireless communication applications. Specific applications that can benefit from millimeter wave integrated NEMS resonators include ultra wideband chip level filters for emerging wireless G and higher versions, chip level sensors for room temperature quantum sensing, and chip level UHF sources for spectroscopic applications.