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2
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2142640460
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note
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2O molecules react with crack-bridging Si-O-Si bonds and create two Si-O-H surface groups, with localized crack extension (27).
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3
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0036506588
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A. M. Fitzgerald, R. S. Iyer, R. H. Dauskardt, T. W. Kenny, J. Mater. Res. 17, 683 (2002).
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(2002)
J. Mater. Res.
, vol.17
, pp. 683
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Fitzgerald, A.M.1
Iyer, R.S.2
Dauskardt, R.H.3
Kenny, T.W.4
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8
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33746470278
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H. Kahn, R. Ballarini, R. L. Mullen, A. H. Heuer, Proc. R. Soc. London Ser. A 455, 3807 (1999).
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(1999)
Proc. R. Soc. London Ser. A
, vol.455
, pp. 3807
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Kahn, H.1
Ballarini, R.2
Mullen, R.L.3
Heuer, A.H.4
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11
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0035773923
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J. Bagdahn, J. Schischka, M. Petzold, W. N. Sharpe Jr., Proc. SPIE 4558, 159 (2001).
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(2001)
Proc. SPIE
, vol.4558
, pp. 159
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Bagdahn, J.1
Schischka, J.2
Petzold, M.3
Sharpe W.N., Jr.4
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12
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2142699661
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note
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The growth of a thin oxide layer on silicon at room temperature, sometimes called a "native oxide," is well established (28). It typically becomes ∼2 nm thick after exposure to air and gradually thickens to a maximum of ∼4 nm.
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14
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0016092601
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S. M. Wiederhorn, H. Johnson, A. M. Diness, A. H. Heuer, J. Am. Ceram. Soc. 57, 336 (1974).
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(1974)
J. Am. Ceram. Soc.
, vol.57
, pp. 336
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Wiederhorn, S.M.1
Johnson, H.2
Diness, A.M.3
Heuer, A.H.4
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15
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2142708239
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note
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2 layer beneath the fabricated structures, which allows portions of a device to be free from the substrate while remaining anchored at discrete points. The details of our MEMS fabrication can be found in (8).
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16
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0034469351
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J. Yang, H. Kahn, S. M. Phillips, A. H. Heuer, J. Microelectromech. Syst. 9, 485 (2000).
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(2000)
J. Microelectromech. Syst.
, vol.9
, pp. 485
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Yang, J.1
Kahn, H.2
Phillips, S.M.3
Heuer, A.H.4
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17
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2142658952
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note
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Three polysilicon films were used in this investigation. Two were 3.0 μm thick and deposited with LPCVD at 580°C. This deposition temperature results in an as-deposited residual tensile stress of ∼300 MPa. The first film was annealed at 910°C in argon, and the residual stress was reduced to 69 MPa. The second film was annealed for a longer time at 910°C in argon, and the residual stress was reduced to 56 MPa. The third polysilicon film was a 3.7-μm-thick multilayer and consisted of nine layers, each between 0.2 and 0.8 μm thick. This film was deposited at alternating temperatures of 570°C and 615°C, as described in (16). The layers deposited at 570°C contained tensile residual stresses on the order of 300 MPa, and the layers deposited at 615°C contained compressive residual stresses, also on the order of 300 MPa. The overall residual stress of the as-deposited multilayer was 69 MPa, but after annealing at 1000°C in nitrogen, the overall residual stress decreased to 44 MPa. The stresses of the individual layers probably differ from the overall value. However, these local stresses do not affect the behavior of the crack tips in these multilayer polysilicon films, as was confirmed by fracture toughness investigations of polysilicon films of varying microstructures, as described in (25).
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18
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2142812512
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IC with modest crack extension.
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20
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2142706770
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note
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IC.
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21
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2142811124
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note
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The procedure for this experiment is described as follows. The actuators were mechanically displaced to produce a tensile stress at the notch tip of 3.6 GPa. Next, a dc voltage was applied between the actuator and the substrate, clamping the actuator to the substrate, and a drop of water was placed on the actuator. When the water evaporated, the capillary forces brought the actuator and substrate into intimate contact, generating van der Waals forces. These forces, sometimes referred to as "stiction" in the micromachining literature, are quite strong when compared to the size of the devices, and they secured the actuator permanently in place, even when the voltage was removed.
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22
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2142813924
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As the applied dc bias voltage causes the actuator to deflect, this increases the stiffness of the actuator support beams, causing small changes in the resonant frequency of the microdevice.
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23
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2142716926
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4 cycles.
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24
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2142754063
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note
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For a semicircular flaw, k = 0.71 (30).
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25
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8844225612
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C. L. Muhlstein, S. B. Brown, Eds, (American Society for Testing and Materials, West Conshohocken, PA)
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R. Ballarini, H. Kahn, N. Tayebi, A. H. Heuer, in Mechanical Properties of Structural Films, ASTM STP 1413, C. L. Muhlstein, S. B. Brown, Eds, (American Society for Testing and Materials, West Conshohocken, PA, 2001), pp. 37-51.
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(2001)
Mechanical Properties of Structural Films, ASTM STP 1413
, pp. 37-51
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Ballarini, R.1
Kahn, H.2
Tayebi, N.3
Heuer, A.H.4
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26
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2142714100
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note
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Although the five specimens tested with R > 0 (tensile stresses only) appeared to exhibit strengths greater than the measured monotonic bend strength, these five data varied between 4.3 and 5.3 GPa. In comparison, the nine samples tested under monotonic loading had strengths between 3.0 and 4.8 GPa. We think that these differences are merely statistical and reflect the vagaries of processing brittle materials such as silicon; Eq. 1 indicates that the flaw size corresponding to a strength of 3.0 GPa is 35 nm, whereas the flaw size that corresponds to a strength of 5.3 GPa is 11 nm. When taken as a single population, the 14 measurements obey Weibull statistics, with a mean strength of 4.3 GPa and a Weibull modulus of 6.3.
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31
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2142655970
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note
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We thank Y. Wang for the finite element analysis of the doubly clamped beams. This work was supported by the Defense Advanced Research Projects Agency under contract N00014-00-1-0881.
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