Tantalum oxide thin films as protective coatings for sensors

Carsten Christensen; Roger De Reus; Siebe Bouwstra

doi:10.1109/MEMSYS.1999.746832

Tantalum oxide thin films as protective coatings for sensors

Carsten Christensen, Roger De Reus, Siebe Bouwstra

Research output: Chapter in Book/Report/Conference proceeding › Article in proceedings › Research › peer-review

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Abstract

Reactively sputtered tantalum oxide thin-films have been investigated as protective coating for aggressive media exposed sensors. Tantalum oxide is shown to be chemically very robust. The etch rate in aqueous potassium hydroxide with pH 11 at 140°C is lower than 0.008 Å/h. Etching in liquids with pH values in the range from pH 2-11 have generally given etch rates below 0.04 Å/h. On the other hand patterning is possible in hydrofluoric acid. Further, the passivation behaviour of amorphous tantalum oxide and polycrystalline Ta2O5 is different in buffered hydrofluoric acid. By ex-situ annealing in O2 the residual thin-film stress can be altered from compressive to tensile and annealing at 450°C for 30 minutes gives a stress-free film. The step coverage of the sputter deposited amorphous tantalum oxide is reasonable, but metallisation lines are hard to cover. Sputtered tantalum oxide exhibits high dielectric strength and the pinhole density for 0.5 μm thick films is below 3 cm-2

Original language	English
Title of host publication	Twelfth IEEE International Conference on Micro Electro Mechanical Systems, 1999. MEMS '99.
Publisher	IEEE
Publication date	1999
Pages	267-272
ISBN (Print)	0-7803-5194-0
DOIs	https://doi.org/10.1109/MEMSYS.1999.746832
Publication status	Published - 1999
Event	Twelfth IEEE International Conference on Micro Electro Mechanical Systems 1999 - Orlando, United States Duration: 17 Jan 1999 → 21 Jan 1999 Conference number: 12

Conference

Conference	Twelfth IEEE International Conference on Micro Electro Mechanical Systems 1999
Number	12
Country/Territory	United States
City	Orlando
Period	17/01/1999 → 21/01/1999

Series	International Conference on Micro Electro Mechanical Systems
ISSN	1084-6999

Bibliographical note

Copyright 1999 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.

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title = "Tantalum oxide thin films as protective coatings for sensors",

abstract = "Reactively sputtered tantalum oxide thin-films have been investigated as protective coating for aggressive media exposed sensors. Tantalum oxide is shown to be chemically very robust. The etch rate in aqueous potassium hydroxide with pH 11 at 140°C is lower than 0.008 {\AA}/h. Etching in liquids with pH values in the range from pH 2-11 have generally given etch rates below 0.04 {\AA}/h. On the other hand patterning is possible in hydrofluoric acid. Further, the passivation behaviour of amorphous tantalum oxide and polycrystalline Ta2O5 is different in buffered hydrofluoric acid. By ex-situ annealing in O2 the residual thin-film stress can be altered from compressive to tensile and annealing at 450°C for 30 minutes gives a stress-free film. The step coverage of the sputter deposited amorphous tantalum oxide is reasonable, but metallisation lines are hard to cover. Sputtered tantalum oxide exhibits high dielectric strength and the pinhole density for 0.5 μm thick films is below 3 cm-2",

author = "Carsten Christensen and Reus, {Roger De} and Siebe Bouwstra",

note = "Copyright 1999 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.; Twelfth IEEE International Conference on Micro Electro Mechanical Systems 1999, MEMS '99 ; Conference date: 17-01-1999 Through 21-01-1999",

year = "1999",

doi = "10.1109/MEMSYS.1999.746832",

language = "English",

isbn = "0-7803-5194-0",

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publisher = "IEEE",

pages = "267--272",

booktitle = "Twelfth IEEE International Conference on Micro Electro Mechanical Systems, 1999. MEMS '99.",

address = "United States",

}

Christensen, C, Reus, RD & Bouwstra, S 1999, Tantalum oxide thin films as protective coatings for sensors. in Twelfth IEEE International Conference on Micro Electro Mechanical Systems, 1999. MEMS '99.. IEEE, International Conference on Micro Electro Mechanical Systems, pp. 267-272, Twelfth IEEE International Conference on Micro Electro Mechanical Systems 1999, Orlando, Florida, United States, 17/01/1999. https://doi.org/10.1109/MEMSYS.1999.746832

Tantalum oxide thin films as protective coatings for sensors. / Christensen, Carsten; Reus, Roger De; Bouwstra, Siebe.
Twelfth IEEE International Conference on Micro Electro Mechanical Systems, 1999. MEMS '99.. IEEE, 1999. p. 267-272 (International Conference on Micro Electro Mechanical Systems).

Research output: Chapter in Book/Report/Conference proceeding › Article in proceedings › Research › peer-review

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N2 - Reactively sputtered tantalum oxide thin-films have been investigated as protective coating for aggressive media exposed sensors. Tantalum oxide is shown to be chemically very robust. The etch rate in aqueous potassium hydroxide with pH 11 at 140°C is lower than 0.008 Å/h. Etching in liquids with pH values in the range from pH 2-11 have generally given etch rates below 0.04 Å/h. On the other hand patterning is possible in hydrofluoric acid. Further, the passivation behaviour of amorphous tantalum oxide and polycrystalline Ta2O5 is different in buffered hydrofluoric acid. By ex-situ annealing in O2 the residual thin-film stress can be altered from compressive to tensile and annealing at 450°C for 30 minutes gives a stress-free film. The step coverage of the sputter deposited amorphous tantalum oxide is reasonable, but metallisation lines are hard to cover. Sputtered tantalum oxide exhibits high dielectric strength and the pinhole density for 0.5 μm thick films is below 3 cm-2

AB - Reactively sputtered tantalum oxide thin-films have been investigated as protective coating for aggressive media exposed sensors. Tantalum oxide is shown to be chemically very robust. The etch rate in aqueous potassium hydroxide with pH 11 at 140°C is lower than 0.008 Å/h. Etching in liquids with pH values in the range from pH 2-11 have generally given etch rates below 0.04 Å/h. On the other hand patterning is possible in hydrofluoric acid. Further, the passivation behaviour of amorphous tantalum oxide and polycrystalline Ta2O5 is different in buffered hydrofluoric acid. By ex-situ annealing in O2 the residual thin-film stress can be altered from compressive to tensile and annealing at 450°C for 30 minutes gives a stress-free film. The step coverage of the sputter deposited amorphous tantalum oxide is reasonable, but metallisation lines are hard to cover. Sputtered tantalum oxide exhibits high dielectric strength and the pinhole density for 0.5 μm thick films is below 3 cm-2

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Tantalum oxide thin films as protective coatings for sensors

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