Design and Fabrication of Nanoscale IDTs Using Electron Beam Technology for High‐Frequency SAW Devices

Abstract

High-frequency Rayleigh-mode surface acoustic wave (SAW) devices were fabricated for 4G mobile telecommunications. The RF magnetron sputtering method was adopted to grow piezoelectric aluminum nitride (AlN) thin films on the Si3N4/Si substrates. The influence of sputtering parameters on the crystalline characteristics of AlN thin films was investigated. The interdigital transducer electrodes (IDTs) of aluminum (Al) were then fabricated onto the AlN surfaces by using the electron beam (e-beam) direct write lithography method to form the Al/AlN/Si3N4/Si structured SAW devices. The Al electrodes were adopted owing to its low resistivity, low cost, and low density of the material. For 4G applications in mobile telecommunications, the line widths of 937 nm, 750 nm, 562 nm, and 375 nm of IDTs were designed. Preferred orientation and crystalline properties of AlN thin films were determined by X-ray diffraction using a Siemens XRD-8 with CuKαradiation. Additionally, the cross-sectional images of AlN thin films were obtained by scanning electron microscope. Finally, the frequency responses of high-frequency SAW devices were measured using the E5071C network analyzer. The center frequencies of the high-frequency Rayleigh-mode SAW devices of 1.36 GHz, 1.81 GHz, 2.37 GHz, and 3.74 GHz are obtained. This study demonstrates that the proposed processing method significantly contributes to high-frequency SAW devices for wireless communications.

Reactive Sputtering of Aluminum Nitride (002) Thin Films for Piezoelectric Applications: A Review

“…It was also reported that when the sputtering pressure increased, the collision between sputtering particles and Ar ions led to the formation of AlN (100) films [ 64 ]. Both observations have been reported by many researchers in Table 2 such as in references [ 17 , 22 , 28 , 35 , 39 , 41 , 45 ].…”

“…For each parameter, selected works that investigate its effect will be mentioned. In addition to using the works that were already summarized in Table 2 , i.e., references [ 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 ], we also highlight additional articles that are not included in that table i.e., references [ 63 , 64 , 65 , 66 , 67 , 68 , 69 , …”

“…From experimental point of view, this is the easiest parameter to manipulate. Therefore, many research groups from Table 2 investigated the effect of this parameters towards producing highly c-axis AlN film [ 20 , 22 , 27 , 39 , 41 , 43 , 45 , 48 , 54 , 61 ]. A higher sputtering power means higher kinetic energies being supplied to the ions.…”

The Bragg Reflector Layer of Low Surface Roughness Based on Solidly Mounted Resonators

“…The global systems for mobile communication could be classified into four types of systems, GSM850/GSM900 band, DCS (GSM1800), WCDMA, and LTE. Thence, several acoustic devices were investigated for high frequency band such as nano-scaled surface acoustic wave (SAW) resonator (1) , thin-film bulk acoustic resonator (TFBAR) (2,3) and SMR.…”

Flexible Tactile Sensors Using AlN and MOSFETs Based Ultra-Thin Chips

“…as it exhibits efficient piezoelectric and dielectric properties, high thermal stability, as well as low dielectric loss tangent and high signal to noise ratio [35][36][37]. Additionally, no poling or stretching is needed [38].…”