DocumentCode :
854494
Title :
New low-stress PECVD poly-SiGe Layers for MEMS
Author :
Rusu, Cristina ; Sedky, Sherif ; Parmentier, Brigette ; Verbist, Agnes ; Richard, Olivier ; Brijs, Bert ; Geenen, Luc ; Witvrouw, Ann ; Lärmer, Franz ; Fischer, Frank ; Kronmüller, Silvia ; Leca, Victor ; Otter, Bert
Author_Institution :
MS/SSM Group, IMEC, Leuven, Belgium
Volume :
12
Issue :
6
fYear :
2003
Firstpage :
816
Lastpage :
825
Abstract :
Thick poly-SiGe layers, deposited by plasma-enhanced chemical vapor deposition (PECVD), are very promising structural layers for use in microaccelerometers, microgyroscopes or for thin-film encapsulation, especially for applications where the thermal budget is limited. In this work it is shown for the first time that these layers are an attractive alternative to low-pressure CVD (LPCVD) poly-Si or poly-SiGe because of their high growth rate (100-200 nm/min) and low deposition temperature (520°C-590°C). The combination of both of these features is impossible to achieve with either LPCVD SiGe (2-30 nm/min growth rate) or LPCVD poly-Si (annealing temperature higher than 900°C to achieve structural layer having low tensile stress). Additional advantages are that no nucleation layer is needed (deposition directly on SiO2 is possible) and that the as-deposited layers are polycrystalline. No stress or dopant activation anneal of the structural layer is needed since in situ phosphorus doping gives an as-deposited tensile stress down to 20 MPa, and a resistivity of 10 mΩ-cm to 30 mΩ-cm. With in situ boron doping, resistivities down to 0.6 mΩ-cm are possible. The use of these films as an encapsulation layer above an accelerometer is shown.
Keywords :
Ge-Si alloys; accelerometers; annealing; electrical resistivity; encapsulation; internal stresses; microsensors; plasma CVD; plasma CVD coatings; semiconductor growth; semiconductor thin films; surface roughness; 10 to 30 mohmcm; 520 to 590 C; MEMS; SiGe; XRD pattern; accelerometer; annealing temperature; as-deposited layers; electrical resistivity; encapsulation layer; encapsulation membrane; high deposition rate; in situ doping; low-stress polycrystalline layer; plasma-enhanced chemical vapor deposition; surface roughness; tensile stress; Annealing; Chemical vapor deposition; Conductivity; Doping; Encapsulation; Micromechanical devices; Plasma applications; Plasma chemistry; Plasma temperature; Tensile stress;
fLanguage :
English
Journal_Title :
Microelectromechanical Systems, Journal of
Publisher :
ieee
ISSN :
1057-7157
Type :
jour
DOI :
10.1109/JMEMS.2003.820304
Filename :
1257359
Link To Document :
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