Residual stress analysis of aluminum nitride piezoelectric micromachined ultrasonic transducers using Raman spectroscopy

In this study, the Raman biaxial stress coefficients KII and strain-free phonon frequencies ω0 have been determined for the E2 (low), E2 (high), and A1 (LO) phonon modes of aluminum nitride, AlN, using both experimental and theoretical approaches. The E2 (high) mode of AlN is recommended for the residual stress analysis of AlN due to its high sensitivity and the largest signal-to-noise ratio among the studied modes. The E2 (high) Raman biaxial stress coefficient of -3.8 cm-1/GPa and strain-free phonon frequency of 656.68 cm-1 were then applied to perform both macroscopic and microscopic stress mappings. For macroscopic stress evaluation, the spatial variation of residual stress was measured across an AlN-on-Si wafer prepared by sputter deposition. A cross-wafer variation in residual stress of ∼150 MPa was observed regardless of the average stress state of the film. Microscopic stress evaluation was performed on AlN piezoelectric micromachined ultrasonic transducers (pMUTs) with submicrometer spatial resolution. These measurements were used to assess the effect of device fabrication on residual stress distribution in an individual pMUT and the effect of residual stress on the resonance frequency. At ∼20 μm directly outside the outer edge of the pMUT electrode, a large lateral spatial variation in residual stress of ∼100 MPa was measured, highlighting the impact of metallization structures on residual stress in the AlN film.



Work Title Residual stress analysis of aluminum nitride piezoelectric micromachined ultrasonic transducers using Raman spectroscopy
Open Access
  1. James Spencer Lundh
  2. Kathleen Coleman
  3. Yiwen Song
  4. Benjamin A. Griffin
  5. Giovanni Esteves
  6. Erica A. Douglas
  7. Adam Edstrand
  8. Stefan C. Badescu
  9. Elizabeth A. Moore
  10. Jacob H. Leach
  11. Baxter Moody
  12. Susan E. Trolier-McKinstry
  13. Sukwon Choi
License In Copyright (Rights Reserved)
Work Type Article
  1. Journal of Applied Physics
Publication Date July 28, 2021
Publisher Identifier (DOI)
Deposited December 08, 2021




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Work History

Version 1

  • Created
  • Added Residual_Stress_Analysis_of_Aluminum_Nitride_Piezoelectric_Micromachined_Ultrasonic_Transducers_Using_Raman_Spectroscopy-JAP-2021.pdf
  • Added Creator James Spencer Lundh
  • Added Creator Kathleen Coleman
  • Added Creator Yiwen Song
  • Added Creator Benjamin A. Griffin
  • Added Creator Giovanni Esteves
  • Added Creator Erica A. Douglas
  • Added Creator Adam Edstrand
  • Added Creator Stefan C. Badescu
  • Added Creator Elizabeth A. Moore
  • Added Creator Jacob H. Leach
  • Added Creator Baxter Moody
  • Added Creator Susan E. Trolier-McKinstry
  • Added Creator Sukwon Choi
  • Published
  • Updated
  • Updated