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A Method for Tapered Deep Reactive Ion Etching using a Modified Bosch Process
KTH, School of Electrical Engineering (EES), Microsystem Technology.
KTH, School of Electrical Engineering (EES), Microsystem Technology.
KTH, School of Electrical Engineering (EES), Microsystem Technology.ORCID iD: 0000-0001-9552-4234
2007 (English)In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 17, no 5, 1087-1092 p.Article in journal (Refereed) Published
Abstract [en]

This paper presents a method for etching tapered sidewalls in silicon using deep reactive ion etching. The method is based on consecutive switching between anisotropic etching using the Bosch process and isotropic dry etching. By controlling the etch depths of the anisotropic and isotropic etch sessions, the sidewall angle can be controlled over a relatively large range. Tapered sidewalls are useful in microfabrication processes such as metal coating of 3D structures (e. g. for electrical connections or vias), mold tool fabrication or as a tool to compensate for reentrant etching. The method was tested and characterized by etching basic test structures in silicon wafers. Based on the investigated anisotropic and isotropic etch depths the sidewall angle could be varied between 0 degrees (straight vertical) and 36 degrees. The sidewall angle was well predicted by a model using the etch depths as parameters. Due to the alternating etch procedure a scalloping pattern is generated on the sidewalls. By frequent switching and short etch sessions this scalloping can be reduced to less than 1 mu m. The process represents an easy method to tailor the sidewall angle in deep etching of silicon. The etch scheme is run in a single etch system and can be implemented in ICP systems of most manufactures. The method can also be used in conjunction with the standard Bosch process as demonstrated herein, where the method was applied to compensate for reentrant etching of high out-of-plane mesa-structures.

Place, publisher, year, edition, pages
2007. Vol. 17, no 5, 1087-1092 p.
Keyword [en]
Engineering, Electrical & Electronic; Nanoscience & Nanotechnology; Instruments & Instrumentation; Materials Science, Multidisciplinary; Mechanics
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-7459DOI: 10.1088/0960-1317/17/5/031ISI: 000246551600033Scopus ID: 2-s2.0-34247505036OAI: oai:DiVA.org:kth-7459DiVA: diva2:12490
Note
QC 20100624Available from: 2007-09-10 Created: 2007-09-10 Last updated: 2010-08-24Bibliographically approved
In thesis
1. A Fully Integrated Microneedle-based Transdermal Drug Delivery System
Open this publication in new window or tab >>A Fully Integrated Microneedle-based Transdermal Drug Delivery System
2007 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Patch-based transdermal drug delivery offers a convenient way to administer drugs without the drawbacks of standard hypodermic injections relating to issues such as patient acceptability and injection safety. However, conventional transdermal drug delivery is limited to therapeutics where the drug can diffuse across the skin barrier. By using miniaturized needles, a pathway into the human body can be established which allow transport of macromolecular drugs such as insulins or vaccines. These microneedles only penetrate the outermost skin layers, superficial enough not to reach the nerve receptors of the lower skin. Thus, microneedle insertions are perceived as painless.

The thesis presents research in the field of microneedle-based drug delivery with the specific aim of investigating a microneedle-based transdermal patch concept. To enable controllable drug infusion and still maintain an unobtrusive and easy-to-use, patch-like design, the system includes a small active dispenser mechanism. The dispenser is based on a novel thermal actuator consisting of highly expandable microspheres. When actuated, the microspheres expand into a liquid reservoir and, subsequently, dispense stored liquid through outlet holes.

The microneedles are fabricated in monocrystalline silicon by Deep Reactive Ion Etching. The needles are organized in arrays situated on a chip. To allow active delivery, the microneedles are hollow with the needle bore-opening located on the side of the needle. This way, the needle can have a sharp and well-defined needle tip. A sharp needle is a further requirement to achieve microneedle insertion into skin by hand.

The thesis presents fabrication and evaluation of both the microneedle structure and the transdermal patch as such. Issues such as penetration reliability, liquid delivery into the skin and microneedle packaging are discussed. The microneedle patch was also tested and studied in vivo for insulin delivery. Results show that intradermal administration with microneedles give rise to similar insulin concentration as standard subcutaneous delivery with the same dose rate.

Place, publisher, year, edition, pages
Stockholm: KTH, 2007. x, 82 p.
Series
Trita-EE, ISSN 1653-5146 ; 2007:046
Keyword
Microneedle, Transdermal, Intradermal, Drug delivery, DRIE, MEMS, Microsystem
National Category
Biomedical Laboratory Science/Technology
Identifiers
urn:nbn:se:kth:diva-4484 (URN)978-91-7178-751-4 (ISBN)
Public defence
2007-09-28, F3, Lindstedsvägen 26, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20100623Available from: 2007-09-10 Created: 2007-09-10 Last updated: 2010-06-28Bibliographically approved

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