AVS 50th International Symposium
    Thin Films Monday Sessions
       Session TF-MoA

Paper TF-MoA5
Al@sub 2@O@sub 3@ Atomic Layer Deposition for the Enhancement of MEMS Performance and Reliability

Monday, November 3, 2003, 3:20 pm, Room 329

Session: Atomic Layer Deposition and Low-k
Presenter: C.F. Herrmann, University of Colorado
Authors: C.F. Herrmann, University of Colorado
N.D. Hoivik, University of Colorado
F.W. DelRio, University of Colorado
V.M. Bright, University of Colorado
Y.C. Lee, University of Colorado
S.M. George, University of Colorado
Correspondent: Click to Email
Ultrathin and conformal films deposited using Atomic Layer Deposition (ALD) can enhance the reliability and performance of MEMS devices. Al@sub 2@O@sub 3@ ALD films are particularly useful because the Al@sub 2@O@sub 3@ ALD surface chemistry is very favorable and amenable to growth on a wide variety of substrates. Al@sub 2@O@sub 3@ ALD films on electrostatically-actuated polysilicon cantilever switches were found to prevent electrical shorting and increase the number of actuation cycles before device failure. In addition, the resonant frequencies of the cantilever beams were also increased by Al@sub 2@O@sub 3@ ALD films resulting from added stiffness. ALD can also be utilized to deposit robust and reliable hydrophobic coatings. The initial MEMS device is optimized for hydrophobic precursor attachment by: 1) covering the MEMS surface uniformly with a continuous adhesion layer; 2) providing a high surface coverage of hydroxyl groups for maximum precursor attachment; and 3) smoothing and removing nanometer-sized capillaries that may otherwise lead to microcapillaries and stiction problems. Quartz crystal microbalance (QCM) studies have been used to monitor the attachment of various chlorosilane and dialkylaminosilane hydrophobic precursors on the Al@sub 2@O@sub 3@ ALD adhesion layer. The QCM results are consistent with the deposition of a dense hydrophobic film on the Al@sub 2@O@sub 3@ adhesion layer. The hydrophobic films on Al@sub 2@O@sub 3@ ALD adhesion layers on silicon wafers were observed to increase dramatically the contact angle. The film properties and adhesion energies were also measured for hydrophobic films on MEMS cantilever beams. After submersion in water, the hydrophobic-coated beams showed much less stiction than the uncoated beams.