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Control of Stress in a Metal–Nitride–Metal Sandwich for CMOS-Compatible Surface Micromachining

Published online by Cambridge University Press:  01 February 2011

Rhodri R. Davies ,
David J. Combes ,
Mark E. McNie  and
Kevin M Brunson
Rhodri R. Davies
Affiliation:
QinetiQ Ltd., St. Andrews Road, Malvern, Worcestershire, WR14 3PS, U.K.
David J. Combes
Affiliation:
QinetiQ Ltd., St. Andrews Road, Malvern, Worcestershire, WR14 3PS, U.K.
Mark E. McNie
Affiliation:
QinetiQ Ltd., St. Andrews Road, Malvern, Worcestershire, WR14 3PS, U.K.
Kevin M Brunson
Affiliation:
QinetiQ Ltd., St. Andrews Road, Malvern, Worcestershire, WR14 3PS, U.K.
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Abstract

Further to previous work, which demonstrated the ability to engineer the in- and out-of-plane stress components in PECVD silicon nitride, this paper reports on the control of stress in a metal-nitride-metal sandwich. The addition of a symmetric metallisation to the core nitride layer provides additional functionality by enabling electrical connectivity and electrostatic transduction. This represents a widely applicable structural layer for CMOS-compatible surface micromachining.

The use of advanced test structures coupled with wafer curvature measurements has allowed for detailed analysis of the stress components within the metal-nitride-metal sandwich and enables predictive engineering of the mechanical properties of the structural layer. Relationships between the in- and out-of-plane stress components of the metal-nitride-metal sandwich as a function of the nitride RF deposition power are reported and discussed. In comparison to values measured for nitride-only, a -30MPa/μm stress gradient offset is observed. A mechanism for the decrease in the stress gradient with the addition of the metallisation is proposed and compares well to modelling.

The optimised metal-nitride-metal sandwich can be repeatably engineered to realise low tensile in-plane stress (100MPa) and low out-of-plane stress gradient (0 ± 10MPa/μm). The effective Young's Modulus of the metal-nitride-metal sandwich was determined to be 150GPa; and a value of 195GPa was calculated for the nitride layer using analytical modelling. Work to further reduce the in-plane stress whilst maintaining low stress gradient is in progress by independently tuning the strain of the metal layers.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 782: Symposium A – Micro- and Nanosystems , 2003 , A8.5
Copyright
Copyright © Materials Research Society 2004

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References

REFERENCES

[1] Smith, J, Montague, S, Sniegowski, J, Murray, J and McWhorter, P, “Embedded micromechanical devices for the monolithic integration of MEMS with CMOS”, Proc. International Electron Devices Meeting (IEDM), Dec. 1995, Washington (USA), pp. 609–612 Google Scholar
[2] Chau, K, Lewis, S, Zhao, Y, Howe, R, Bart, S and Marcheselli, R, “An integrated force-balanced capacitive accelerometer for low-g applications”, Proc. Int. Conf. on Solid-State Sensor and Actuators (Transducers'95), Jun. 1995, Stockholm (Sweden), pp. 593–596 Google Scholar
[3] King, D O, Ward, M C L, Brunson, K M and Hamilton, D J, “Polysilicon process development for a fully integrated surface micromachined accelerometer with CMOS electronics”, Sensors & Actuators A–68, 1998, pp. 238–243 Google Scholar
[4] Noble, R A, Davies, R R, McIntosh, J, Hutchins, D, Robertson, T and Saul, P, “A cost-effective and manufacturable route to the fabrication of high-density 2D micromachined ultrasonic transducer arrays and (CMOS) signal conditioning electronics on the same silicon substrate”, IEEE International Ultrasonics Symposium, Oct. 2001, Atlanta (USA), pp. 941–944 Google Scholar
[5] Davies, R R, Brunson, K M, McNie, M and Combes, D J, “Engineering In- and Out-of-Plane Stress in PECVD Silicon Nitride for CMOS-Compatible Surface Micromachining”, SPIE International Symposium on Micromachining and Microfabrication, Oct. 2001, California (USA), pp. 320–328 Google Scholar
[6] Gianchandani, Y B and Najafi, K, “Bent-Beam Strain Sensors”, Journal of Microelectromechanical Systems 56–1, 1996, pp. 52–58 Google Scholar
[7] DeVoe, D L and Pisano, A P, “Modeling and Optimal Design of Piezoelectric Cantilever Microactuators”, Journal of Microelectromechanical Systems 6–3, 1997, pp. 266–270 Google Scholar
[8] Kim, D-K, Heiland, B, Nix, W D, Arzt, E, Deal, M D and Plummer, J D, “Microstructure of thermal hillocks on blanket Al thin films”, Thin Solid Films 371, 2000, pp. 278–282 Google Scholar
[9] McNie, M E, King, D O, Brunson, K M, Davies, R R, Price, N, Hsu, C, Bart, S F and van Kuijk, J, “Software-based design kits for improved microsystems design in a verified simulation environment”, Eurosensors XIV, Aug. 2000, Copenhagen (Denmark), pp. 715718 Google Scholar
[10] EUROPRACTICE web site: www.europractice.com Google Scholar