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MEMS MATERIALS

Y.C. TaiCaltech Micromachining Lab. 2. MEMS Material. Electrical Properties -- available data base from ICChemical Properties -- available data base from ICMechanical Properties ? usually lack of data base-- Young's modulus, Ey-- Poisson's ration, n-- Residual stress, s-- Fracture str

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MEMS MATERIALS

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    1. Y.C. Tai Caltech Micromachining Lab 1 MEMS MATERIALS

    2. Y.C. Tai Caltech Micromachining Lab 2 MEMS Material Electrical Properties -- available data base from IC Chemical Properties -- available data base from IC Mechanical Properties – usually lack of data base -- Young’s modulus, Ey -- Poisson’s ration, n -- Residual stress, s -- Fracture strength, sf -- Fatigue?

    3. Y.C. Tai Caltech Micromachining Lab 3 Single-Crystal Silicon (1) Diamond-structure with 8 atoms per cell. Lattice spacing = 5.43 Å at room temp. Brittle material, but will plastically deform when stressed at high temperature (>900°C).

    4. Y.C. Tai Caltech Micromachining Lab 4 Single-Crystal Silicon (2)

    5. Y.C. Tai Caltech Micromachining Lab 5 Polycrystalline Silicon (Polysilicon) Ideal Properties Zero built-in stress & stress gradient Predictable mechanical & electrical properties Achievable Properties: Built-in stress = –20 MPa, near-zero gradient E = 160 ± 10 GPa, grain sizes, orientation controllable Conductivity = 0.1 mW·cm to intrinsic

    6. Y.C. Tai Caltech Micromachining Lab 6 Best Mechanical Properties achieved by Deposition Temperature: Just below the amorphous-to-crystalline transition (590°C) followed by annealing at 1050°C for 1 hour. Deposition Pressure: 200 ± 50 mTorr Deposition Chemistry: SiH4 diluted in H2 carrier, undoped or post-dep doped. Results: Built-in stress at –20 MPa Best film uniformity, quality, and step coverage Random crystallite orientation Þ isotropic mechanical properties

    7. Y.C. Tai Caltech Micromachining Lab 7

    8. Y.C. Tai Caltech Micromachining Lab 8

    9. Y.C. Tai Caltech Micromachining Lab 9

    10. Y.C. Tai Caltech Micromachining Lab 10

    11. Y.C. Tai Caltech Micromachining Lab 11

    12. Y.C. Tai Caltech Micromachining Lab 12 Other Materials Piezoelectrics: Quartz, ZnO, PZT, AlN SiC: CVD (1,200-1,400°C) Diamond Films: CVD Metals: Al, Ni, NiFe, Cu, Au, Hg Polymers: SU8, Parylene, PDMS

    13. Y.C. Tai Caltech Micromachining Lab 13 Material Testing methods

    14. Y.C. Tai Caltech Micromachining Lab 14 Beam Load-Deflection Method

    15. Y.C. Tai Caltech Micromachining Lab 15 Buckling Fracture Method

    16. Y.C. Tai Caltech Micromachining Lab 16 Wafer Warpage Method

    17. Y.C. Tai Caltech Micromachining Lab 17 Diaphragm Load-Deflection method

    19. Y.C. Tai Caltech Micromachining Lab 19 Electrostatic Pull-in Method

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