Conference paper
Tantalum oxide thin films as protective coatings for sensors
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
| Language: | English |
|---|---|
| Publisher: | IEEE |
| Year: | 1999 |
| Pages: | 248-251 |
| Proceedings: | 9th European Workshop on Micromechanics |
| Series: | International Conference on Micro Electro Mechanical Systems |
| ISBN: | 0780351940 and 9780780351943 |
| ISSN: | 10846999 |
| Types: | Conference paper |
| DOI: | 10.1109/MEMSYS.1999.746832 |
0.5 micron 140 C 450 C Amorphous materials Annealing Chemical sensors Coatings Protection Sputter etching Sputtering Ta/sub 2/O/sub 5/ Tensile stress Thin film sensors Thin films aggressive media exposed sensors amorphous tantalum oxide annealing buffered hydrofluoric acid compressive stress corrosion protective coatings etch rate etching ex-situ annealing high dielectric strength internal stresses microsensor protective coatings microsensors packaging passivation passivation behaviour patterning pinhole density polycrystalline tantalum oxide pressure sensor pressure sensors reactively sputtered thin films residual thin-film stress semiconductor device packaging sputtered coatings step coverage stress-free film tantalum compounds tensile stress
