Study of Porosity Gradient in Released Porous Silicon Microstructures

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Abstract

Porosity gradients are a key factor limiting the application of porous silicon (PS) in micromachined structures. In this work, the in-depth porosity profile of PS was studied by measuring the average porosity for samples grown at both constant current density and varied current density; the latter designed to compensate vertical porosity gradient effects. For constant current density, the results showed that the porosity increases from the top surface toward the Si/PS interface. This result is applicable to samples less than 4-mu m thick. The varied current density investigations with current density reduced over the duration of anodisation indicated that two recipes at Delta I = 10 & 12 mA/cm(2) resulted in a relatively low porosity gradient and low tensile residual stress. Using these two recipes, released MEMS-based PS microstructures were fabricated. The results showed that the recipe using a current density variation of Delta I = 10 mA/cm(2) (where I-initial = 20 mA/cm(2) and I-final = 10 mA/cm(2)) was the best approach to produce microstructures with a peak to valley (PV) flatness of 200 nm. This study provides a pathway to create released, MEMS-based resonant cavity optical devices using only a single material (Si) platform.

Original languageEnglish
Title of host publication2018 Conference on Optoelectronic and Microelectronic Materials and Devices, COMMAD 2018
PublisherIEEE, Institute of Electrical and Electronics Engineers
Pages1-4
Number of pages4
ISBN (Electronic)9781538695241
DOIs
Publication statusPublished - 14 May 2019
Event2018 Conference on Optoelectronic and Microelectronic Materials and Devices, COMMAD 2018 - Perth, Australia
Duration: 9 Dec 201813 Dec 2018

Publication series

Name2018 Conference on Optoelectronic and Microelectronic Materials and Devices, COMMAD 2018

Conference

Conference2018 Conference on Optoelectronic and Microelectronic Materials and Devices, COMMAD 2018
CountryAustralia
CityPerth
Period9/12/1813/12/18

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