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 - 2 Jul 2018
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
Country/TerritoryAustralia
CityPerth
Period9/12/1813/12/18

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