| AVS 60th International Symposium and Exhibition | |
| Electronic Materials and Processing | Thursday Sessions |
| Session EM-ThP |
| Session: | Electronic Materials and Processing Poster Session |
| Presenter: | M.R. King, Northrop Grumman ES |
| Authors: | M.R. King, Northrop Grumman ES B.P. Wagner, Northrop Grumman ES E.B. Jones, Northrop Grumman ES N. El-Hinnawy, Northrop Grumman ES S.R. McLaughlin, Northrop Grumman ES P. Borodulin, Northrop Grumman ES J.S. Mason, Jr., Northrop Grumman ES R.S. Howell, Northrop Grumman ES R.M. Young, Northrop Grumman ES M.J. Lee, Northrop Grumman ES |
| Correspondent: | Click to Email |
Recently the digital memory industry has exploited chalcogenide materials for their distinct phase-dependent electrical properties, where the large resistivity difference between crystalline and amorphous states is used to create efficient memory platforms.
Digital applications primarily require large DC on/off ratios; RF switches on the other hand require very low on-resistance (Ron) and off-capacitance (Coff). These requirements are often mutually exclusive, where gains in one come at the expense of the other. Chalcogenide phase change materials represent a unique solution to this dilemma. With PCM devices, not only is it possible to obtain a very low Ron concomitant with very low Coff, but one can also achieve zero prime power consumption during steady state operation.
This presentation will detail the development of phase change materials that enable world class RF switch performance. Specifically a chalcogenide inline phase change switch (IPCS) utilizing GeTe has been fabricated for the first time utilizing a 3rd terminal for controlling an independent resistive heater to accomplish the thermal actuation of the phase change material. An on-state resistance of 6 Ω (0.06 Ω-mm), with an off-state capacitance and resistance of 33fF and 1 MΩ were measured, respectively, resulting in an RF switch figure-of-merit cut-off frequency (Fco) of 0.7 THz and a switching on/off ratio of 105. The power required to change the GeTe from amorphous to crystalline was as low as 0.5W, with zero power consumption during steady state operation, making it a non-volatile RF switch. To the authors’ knowledge, this is the first reported implementation of an RF phase change switch in a traditional, 3-terminal, in-line configuration.
In order to achieve such a high level of performance, significant material development efforts were undertaken. GeTe films were deposited using the DC magnetron sputtering technique and a power-pressure matrix was utilized to minimize sheet resistivity (Rs) and maximize the on-off ratio. Morphological features were evaluated using XRD, SEM and FIB-based cross sections. Electrical properties of as-deposited GeTe films were evaluated using 4-point probe measurements and a heated stage. The combined effect of sputtering power and pressure on film morphology and material properties will be presented.
In addition to wide ranging morphological and Rs variations with deposition parameters, it was found that the sputtering process significantly affects the chemical susceptibility of the films. An optimized fabrication scheme will be presented, in which high quality GeTe films were capable of being processed without a capping layer.