Air-coupled linear and sparse cMUT array manufactured using MUMPs process

Abstract

An assessment of the standard fabrication Micro-Electro-Mechanical Systems (MEMS) process Multi-User MEMS Processes (MUMPs) for complex air-coupled capacitive Micromachined Ultrasonic Transducer array aperture manufacture is reported. A 1-D linear array and a 2-D sparse symmetric binned-array have been designed and manufactured, and then characterised experimentally using electrical impedance measurements, laser vibrometry and air-coupled field measurement; the experimental data are supported by simulated data using Finite Element technique and field simulation based on Huygens’ principle. A methodology for the manufacture of the array structures using the MUMPs process is described. Electrical characterisation shows the devices operation at 770 kHz and the existence of large parasitic capacitances and electrical losses. Mechanical crosstalk of array substrate has been measured at -40 dB using laser vibrometry. Moreover, the laser vibrometry measurement and the field characteristics of one element reveal that each element operates as a piston radiator

Fabrication of capacitive micromachined ultrasonic transducers based on adhesive wafer bonding technique

“…As a result, CMUTs are an alternative to piezo-based transducers and attract major research interest. Besides medical imaging and NDT, CMUTs were also widely studied for extensive applications such as blood flow measurement, distance sensing, pressure sensing, fluid properties measurement and cancer treatment [3,[13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28].…”

Electromechanical performance comparison for different CMUT element geometries

“…CMUT arrays are made of small elements of a few tens of micron characteristic length, making up an array typically of 100 to 500 micron length. Different geometries of CMUT elements and CMUT arrays have been proposed including circular, square and hexagonal elements and sparse, square matrix [8] and ring arrays [3]. CMUT array optimization techniques have been proposed in [9].…”

“…The use and limitations of commercial MUMPs for CMUT fabrication have been reported in [8,11]. Amongst the most important practical limitations found were those concerning fixed layer thicknesses, fixed polysilicon doping, maximum allowed die size, and the radiation disturbance caused by etch holes and any other acoustical ports present in the design.…”

Droplets, vapours and clouds - A new approach to capacitive transducer manufacture

“…From the simple polishing [1]; micro-machining of silicon [2], [3]; microstereolithography (MSL) [4] or the multiuser MEMS process (mumps) [5]. In any of these techniques the goal is the creation of a regular array of cavities with uniform dimensions, geometry and spatial arrangement.…”