Novel four-port RF phase change switches based on GeTe thin film

Abstract

An indirect-heated phase-change switch using germanium telluride (GeTe) has been fabricated using thermal actuation driven by thin film heater on the model. Switches require a low ON-state resistance and a high OFF-state resistance with OFF/ON resistance ratio of 105. The finite element analysis simulation is applied to simulate the temperature of individual node GeTe with different microwave heating pulses. Finally, in order to reduce the phase-change time and increase the switching speed of indirectly heated switching structures, a new four-port indirectly heated phase change switching structure is proposed. In this paper, the heat dissipation of the switch is increased by etching deep grooves on the back of the switch. This structure obviously reduces the phase change time compared to conventional indirectly heated phase change switches the time between ON-state and OFF-state is reduced by more than 19% and the total process is reduced by more than 47%. The GeTe phase-change switches with etched grooves not only significantly increases the switching speed, but also reduces the risk of recrystallisation of the phase change material.

A Review on Material Selection Benchmarking in GeTe-Based RF Phase-Change Switches for Each Layer

“…Figure 10 c delineates the impact of the switch heater size on insertion loss (IL) and isolation (Iso). These measurement results conform to the trends observed in simulation outcomes from another report, as depicted in Figure 10 d [ 26 ]. Therefore, a preliminary conclusion is drawn that a smaller heater width results in lower IL, and higher Iso and return loss (RL).…”

“…In 2019, Léon et al [ 25 , 26 ] compared two configurations utilizing germanium telluride (GeTe) phase-change-material-based direct heating switches. Employing deep UV lithography stepper technology enabled the definition of consistent patterns with widths as narrow as 250 nm.…”

“…Experiments have demonstrated that TiW, W, TiN, NiCrSi, NiCr, and Mo are all candidates for microheaters in PCSs, as shown Figure 10 a. To achieve the melting point of GeTe, varying widths of heaters with different metal materials were simulated using Comsol 5.5 [ 26 ]. From the simulation result, a wider heater width generates a lower max temperature at constant thickness, and Mo generates more heat than W and Cr.…”

“…( b ) Four-port directly heated model [ 23 ]. ( c ) The image of the four-port planar structure GeTe direct heating switch (adapted from [ 26 ]).…”

“…However, future integration poses a challenge due to the requirement of a laser source. On the other hand, electrical-activated PCSs, categorized based on heating methods, include direct heating [ 18 , 19 , 20 , 21 , 22 ] and indirect heating [ 23 , 24 , 25 , 26 , 27 , 28 ]. These two types of switches will be discussed in more detail in later chapters.…”