PMN–PT (lead magnesium niobate–lead titanate) piezoelectric material micromachining by excimer laser ablation and dry etching (DRIE)

Abstract

In the attempt to find the appropriate micromanufacturing technology of PMN-PT (lead magnesium niobate-lead titanate) piezo material, whose MEMS-related applications look promising, two methods are investigated: excimer laser ablation (using KrF gas) and inductively coupled plasma (ICP) dry etching, also known as DRIE (using Ar/C 4 F 8 gases). The paper quantitatively reports the optimal parameters for PMN-PT micromachining and compares both methods. KrF excimer laser ablation threshold fluence is of 14 J/cm², the etching rate may reach 100 µm/min (50 nm/pulse) but the ablated surfaces are cone-shaped restricting thus the method to cutting/drilling 2D shapes. Excimer ablation method is found to be more convenient for rapid prototyping with less precise features requirements (>10 µm). On the other hand DRIE method on PMN-PT is time-consuming, requires a hard mask deposition but is cleaner and more precise. Dry etching maximum recorded speed is of 0.19 µm/min. The nickel hard mask selectivity varies around 8:1. In exchange this method provides flatter surfaces with no etched material redeposition.

Planar ultrasonic transducer based on a metasurface piezoelectric ring array for subwavelength acoustic focusing in water

“…The density, Poisson's ratio and dielectric constant of MPRA layer (PZT-5H, IStec Co.) are 7600 kg/m 3 , 0.3 and 1900, respectively. Also, the piezoelectric properties, d 33 , d 31 and d 15 of MPRA layer are 411, − 202 and 498 pm/v, respectively. For the impedance matching between water and piezoelectric ring array, the density, Poisson's ratio and Young's modulus of the impedance matching materials (Stycast 2057, Henkel Co.) are 1580 kg/m 3 , 0.45 and 1.7 GPa, respectively.…”

“…When engineering piezoelectric materials, laser ablation methods are found to be more convenient than conventional deep reactive ion etching (DRIE), which takes a long time and requires hard mask deposition for rapid micromachining of complex patterns with precision. Studies in which piezoelectric materials have been processed using laser ablation include one in which PVDF films were patterned with a 193-nm excimer laser to create bioelectronic devices 31 , an investigation into the creation of electrodes on piezoelectric ceramics for sensor applications using ns-pulsed laser ablation 32 , a comparative study on the machinability of lead magnesium niobate-lead titanate using excimer laser ablation and DRIE 33 , and a study on the growth and deposition process of laser-ablation-deposited piezoelectric thin films for piezoelectric microdevices 34 . However, reports on micromachining of complex piezoelectric patterns in an ultrasonic transducer are comparatively few.…”

PMN-PT piezoelectric material and related applications in Silicon-integrated devices like microactuators and energy harvesters

“…Patterning the PMN-PT material will allow novel and complex devices. Some very recent tests referenced in [5] and [6] detail the reactive ion etching (RIE) of PMN-PT using an Argon-based gas combination and the laser ablation using ArF excimer ultraviolet light. …”

Actuated MOEMS Micro-Mirror Based on PMN PT Piezoelectric Material

“…Among the advantages of using PMN-PT we note its ability of being used in bulk [11] and the ease of fabrication [12]. This paper investigates how bulk PMN-PT actuators behave when integrated in MOEMS.…”