本研究的目的在探討將75Fe-22Ni-3Cr (FNC)/64Fe-36Ni (Invar)雙金屬薄膜以無下層支撐結構的自由懸空態(Free-Standing Membrane)應用在微致動器的可行性與性能表現(performance)。

　　在製程技術上，使用表面與體加工技術(surface and bulk micromachine)製作自由懸空以及具下層多晶矽支撐結構的FNC/Poly-Si與Invar/Poly-Si懸臂樑。經由Bulge test與懸臂樑特徵結構來探討FNC/Invar雙層薄膜的機械、熱傳導性質與製程參數、幾何參數間的關係；並結合ANSYS有限元素分析驗證與探討量測值與理論值間的差異。

　　在薄膜的熱穩定性上，FNC/Invar雙層薄膜經歷400℃退火的穩定化後，在約0.1 μm的白金保護層覆蓋下，其微結構、殘留應力與電阻均能在250℃的熱負載循環下維持穩定，沒有顯著的歷程變遷，並且沒有層間擴散的發生。FNC薄膜雖然在退火與熱循環中出現<220>方向的織構，並且發生<211>與<200>方向的晶粒成長，但對薄膜的楊氏模數並未產生明顯的影響。

　　此外FNC/Invar雙層薄膜的殘留應力、微結構與薄膜的濺鍍壓力和薄膜的厚度有明顯的關連。當濺鍍功率為100W時，FNC與Invar薄膜的殘留應力態轉換(壓縮-拉伸)出現在濺鍍壓力30~40 mtorr之間，而造成殘留應力轉換之工作壓力(TP)則隨著濺鍍功率的提升呈線性增加。藉由對濺鍍壓力與功率的控制可使薄膜的殘留應力限定在較低的拉伸應力態(40mtorr, 100W, 68Mpa for FNC/Invar bilayer)，或壓縮應力態。而在固定濺鍍壓力下，FNC與Invar薄膜的拉伸殘留應力與膜厚的關係分別在1.2 μm、0.6 μm呈現一最大值；而雙層薄膜則因介面應力的引入，而使的拉伸應力最大值出現在更高的薄膜厚度，1.4 μm。

　　濺鍍壓力同時也是影響薄膜電阻與熱傳導係數的最重要參數。由
於濺鍍壓力對晶粒尺寸與晶粒型態有直接的關連性，因此熱傳係數隨著晶粒尺寸增大而上升的趨勢可以由濺鍍壓力的變化來得到控制。而薄膜電阻的尺寸效應也同樣受到濺鍍壓力變化的制約。

　　殘留應力與膜厚對FNC/Invar雙層薄膜靜態響應的影響則可分為兩方面說明：膜厚較大時(>1.5 μm)，薄膜結構的撓曲剛性為影響薄膜在壓力與溫度負載下位移響應的主要因素；當膜厚小於1.5 μm時，殘留應力的大小則成為主要的決定因子。由於膜厚同時也是薄膜結構響應時間的變數，本研究對殘留應力-膜厚-位移與膜厚-位移-響應時間的關係作圖，未來在微致動器的設計上，可作為最佳化設計的參考。

　　在本研究中，一厚度3.2 μm，邊長1mm的方形FNC/Invar雙層薄膜，在200℃的溫度負載下，當殘留應力為160Mpa時其位移響應約為15μm，而當殘留應力為壓縮應力且零點位移小於254nm時，則其位移響應可達135 μm。同樣結構在200 mW的輸入功率下，達到飽和撓曲(full deflection)的響應時間約為128 msec。

　　In this study the materials properties and membrane performance of the 75Fe-22Ni-3Cr(FNC)/64Fe-36Ni(Invar) bimetal freestanding mem- brane was investigated.

　　The FNC and Invar films were prepared by DC magnetron sputtering. The test structure for mechanical and thermal properties was fabricated by surface and bulk micromachine techniques. By tuning the sputtering parameters, the effects of microstructure on electrical resistance, thermal conductivity, and mechanical properties were studied. The residual stress and Young’s modulus of the FNC/Invar freestanding membrane were measured by the Bulge test, and the thermal conductivity was measured by a characteristic cantilever beam structure.

　　On the thermal stability, a 400 oC/37 minutes annealing process was sufficient to stabilize the FNC/Invar bimetal membrane. The microstructure, residual stress, electrical resistance and membrane adhesion to the substrate showed no apparent transform from the original state to the state after 100 times thermal cycle in the range of 25oC to 250oC. Although a <220> direction texture was observed after thermal cycle and grain growth on (211) and (200) faces were observed for the FNC membrane, there was no obvious influence on the Young’s modulus of the membrane.

　　The residual stress, microstructure, membrane thickness and deposition pressure (DP) were shown closely correlated in this study.

　　There existed a peak residual stress value for the residual stress- membrane thickness relation. The corresponding thickness of the peak stress was 1.2 and 0.6 μm for FNC and Invar membrane respectively. The corresponding thickness for FNC/Invar bilayer shifted to a higher value, 1.4 μm, with the introduction of interface stress.

　　As the deposition pressure increased from low pressure, such as 5 mtorr, to high pressure, there was a transition from compressive to tensile for the residual stress. The transition pressure of the residual stress for both the FNC and Invar membrane trended to lower deposition pressure as deposition power increased. All the changes in the residual stress states were raised from the deposition pressure dependent microstructure. The microstructure change from dense fibrous structure to coarse columnar grain as the deposition pressure increased.

　　Not only the residual stress was effected by the deposition pressure dependent microstructure, but also the membrane resistance and thermal conductivity was effected. The membrane resistance increased as DP increased for higher DP. High DP might introduce more structure defects therefore the scattering at lattice defects of the conductive electrons was raised. The thermal conductivity of the membrane decreased as DP increased for the same reason of electrical resistance. However that scattered at lattice defects were phonons instead of electrons.

　　The effect of residual stress and membrane thickness on the static response of the FNC/Invar bilayer can be explained from two aspects. For membrane thickness larger than 1.5 μm, the flexural rigidity was the dominated factor for membrane response under thermal and pressure load. For thickness smaller than 1.5 μm, the residual stress level became the dominated one. A square freestanding FNC/Invar bimetal membrane with thickness of 3.2 μm and 1 mm in side length could deflect up to 135 μm in 128 msec under 200 mW input power.

　　Because the response time was a function of many parameters, the relation between residual stresses, membrane thickness, input power, deflection and response time were analyzed in this study for optimal design of microactuator in the future.

1. W. Tang, T. Choung, H. Nguyen, W. Judy, R. Howe, Electrostatic-Comb Drive of Lateral Polysilicon Resonators.”, Sensors and Actuators, A21-A23,(1990) 328

2. M. Shikida, K. Sato, T. Harada, “Fabrication of an Electrostatic Microactuators with an S-Shape Film.”, Tranducers’95, Eurosensors IX, 102-B6,(1995) 426

3. R. Legtenberg, J. W. Berenschot, M. C. Elwenspoek, J. H. J. Fluitman, “Electrostatic Curved Electrode Actuators.”, Proc. MEMS ’95 (1995) 37

4. S. Hoen, P.l Merchant, “Electrostatic Surface Drivers: Theoretical consideration and Fabrication.”, 1997 International Conference on Solid State Sensors and Actuators ,1A3.03 (1997) 41

5. C. Liu, T. Tsao, Y. C. Tai, C. M. Ho, ”Surface Micromachined Magnetic Actuators.” Proc. MEMS’94 Oiso Japan ,(1994) 57

6. I. J Busch-Vishniac, “The Case for Magnetically Driven Microactuators.” Sensors and Actuators, A33 (1992).207

7. C. Teong, I. Busch-Vishniac, ”A Submicron Accuracy Magnetic Levitation Micromachine with Endpoint Detection.” Sensors and Actuators, A29 (1991).225

8. B. Wanger, W. Benecke, G. Engelmann, J. Simon, “Microactuators with Moving Magnets for Linear,Torsional or Mutiaxial Motion.”, Sensors and Actuators, A32 (1991) 598

9. C. Bosch, B. Heimhofer, G. Muck, H. Seidel, U. Thunser, W. Welser, “A Silicon Microvalve with Combined Electromagnetic/Electrostatic Actuation.”. Sensors and Actuators,A37~38 (1993) 684

10. R. Maeda, C. Lee, A. Schroth, “Development of A Micromirror Using Piezoelectric Excited and Actuated Structure.”, Mat.Res.Soc.Symp.Proc. 444 (1996) 223

11. S.M. Sakata, S. Wakabayashi, H. Totani, M. Ikeda,” Basic Characteristics of A Piezoelectric Buckling Type OF Actuators.”, Tranducers’95, Eurosensors IX, 101-PB5,(1995) 422

12. J. G. Smith, ”Piezoelectric Micropump with Three Valves Working Peristaltically ”, Proc. of the 1990 Inter. Conf. on Solid State Sensors and Actuators, (1990).203.

13. S. Shoji, B. van der Schoot, N. de Rooji, M. Esashi, “Smallest Dead Volume Microvalve for Integrated Chemical Analyzing Systems “, Proc. Tranducers’91, San Fransisco, (1991).1052.

14. B. Rashidian, M.G. Allen, “ Intergated Piezoelectric Polymers for Microsensing and Microactuators Applications “, Proc. ASME , DSC-VOL.32 (1991) 171.

15. K. Uchino, “Piezoelectric Ceramics in Smart Actuators and Systems”, First European Conference on Smart Structures and Materials ,(1992) 177

16. S.M. Young, Y. J. Lee, “Interaction of Structure Vibration and Piezoelcctric Actuation “, J. of Smart Materials and Structures, 30(1994) .494.

17. T. Honda, K. J. Arai, M. Yamaguchi, “ Fabrication of Actuators Using Magnetostrictive Thin Films “,Proc. IEEE MEMS, Oiso,Japan,(1994) 51

18. E. Quandt, K. Seemann, “ Fabricaion of Giant Magnetostrictive Thin Films Actuators”, Proc. IEEE MEMS,Amsterdam,Netherlands,(1995) 273

19. N. W. Hagood, E. F. Crawley, J. de Luis, E. H. Anderson, “Development of Integrated Components for Control of Intelligent Structure”, Smart Materials,Structures, and Mathematical Issues,(1988) 81

20. C. M. Friend, “ The Stability of Strain in Shape-Memory Actuators.”, First European Conference on Smart Structures and Materials (1992) 181

21. Mark A. Thrasher, Ali R. Shahin, Peter H. Meckl, James d. Jones, “ Thermal Cycling of Shape Memory Alloy Wires Using Semiconductor Heat Pump Modules”, First European Conference on Smart Structures and Materials,(1992) 197

22. S. Miazaki, K. Nomura, “Development of Perfect Shape Memory Effect in Sputter-Deposited Ti-Ni Thin Films.” ,Proc. IEEE MEMS ’94, (1994) 176

23. M. Kohl, K. D. Skrobanek, “Linear Microactuators Based on the Shape Memory Effect.”, IEEE Tranducers ’97,Chicago US,3A2.04,(1997) 785

24. K. Udayakumar, S. Bart, A. Flynn,J. Cheng, L. Tavrow, L.Cross, R. Brooks, D. Ehrlich, “Ferroelectric Thin Ultrasonic Micromotors. “ Proceeding MEMS ’91, (1991) 109

25. C.Doring, T. Grauer, J. Marek, H. P. Trah, M. Willamann, “Micromachained Thermalelectrically Driven Cantilever Structures for Fluid Injection Deflection “, Proc. IEEE MEMS , Feb. (1992) 12.

26. Van de Pol, F. van Lintel, H.Elwenspoek, J. Fluitman, “A Thermoneumatic Micropump Based on Microengineering Techniques.”, Sensors and Actuators, A21(1990) 198

27. T. Lisec, S. Hoerschelmann, H. J. Quenzer, B. Wanger, W. Beneche,” Thermal Driven Microvalve with Buckling Behavior for Pneumatic Applications. “, Proc. IEEE MEMS ’94,Oiso, Japan, (1994) 13

28. H. P. Trah, H. Baumann, C. Doring, H. Goebel, T. Gauer, M. Mettner,” Micromachine valve with hydraulically actuated membrane subsequent to a thermaelectrically controlled bimorph cantilever.”, Sensors and Actuators, A39(1993) 169

29. H. Matoba, T. Ishikawa, C. J. Kim, R. S. Muller, “ A Bistable Snapping Microactuators.”, Proc. IEEE MEMS ’94 (1994) 45

30. .N. Takeshima, H. Fujita, “Polyimid Bimorph Actuators for Ciliary Motion System.”, Micromechanical Sensors, Actuators and Systems(DSC-Vol.32) ASME Winter Annual Meeting, Atlanta, GA, Dec.(1991) 203.

31. W. Riethmuller, W. Benecke, “Thermally Excited Silicon Microactuators “, IEEE Trans. Electron Devices, Vol35,No.6, June (1988) 758.

32. E. Hashimoto, H. Tanaka, Y. Suzuki, Y. Uenishi, A. Watabe, “Thermally Controlled Magnetization Actuator(TCMA) Using Thermalsensitive Magnetic Materials.”, Proc. IEEE MEMS ’94,(1994) 108

33. Y. Yamagata, T. Higuchi, N. Nakamura, S. Hamamura, “A Micro Mobile Mechanism Using Thermal Expansion and its Theoretical Analysis. “,Proc. IEEE MEMS ’94, Oiso ,Japan,(1994) 142

34. W.Fang, J. A. Wikert, “Post Buckling of Micromachined Beams. “,Proc. IEEE MEMS ’94, Oiso ,Japan, (1994) 182

35. X. Yang, Y. Tai, “Micro Bellow Actuators.”, 1997 Inter. Conf. on Solid-State Sensors and Actuators ,Digest of Technical Papers, 1A3.04, (1997) 45

36. J.H. Comtios, M. A. Michallicek, C. C. Barron, “Characterization of Electrothermal Actuators and Arrays Fabricated in a Four-Level, Planarized Surface-Micromachined Polycrystalline Silicon Process.“, 1997 Inter. Conf. on Solid-State Sensors and Actuators ,Digest of Technical Papers,3A1.05, (1997) 769

37. Shifang Zhou, Xi-Qing Sun, William N. Carr, “A Micro Variable Inductor Chip Using MEMS Relays.”, 1997 Inter. Conf. on Solid-State Sensors and Actuators ,Digest of Technical Papers,4A3.01, (1997) 1137.

38. T. Seki, M. Sakata, T. Nakajima, M. Matsumoto, “ Thermal Buckling Actuators for Micro Relays.”, 1997 Inter. Conf. on Solid-State Sensors and Actuators ,Digest of Technical Papers,4A3.05, (1997) 1153.

39. J. Ji, J. Chaney, M. Kaviany, P. L. Bergstorm, K. D. Wise, “Microactuation Based on Thermally Driven Phase-Change.”, IEEE Transducers ’91, (1991) 1037

40. M. K. Small, J. J. Vlassak, S. F. Powell, B. J. Daniels, William D. Nix, “Accuracy and Reliability of Bulge Test Experiments.”, Mat. Res. Soc. Symp. Proc., 308 (1993) 159

41. M. K. Small, William D. Nix, “Analysis of the Accuracy of the Bulge Test in Determining the Mechanical Properties of Thin Films.”, J.Mater.Res.,Vol.7,.6 (1992) 1553

42. J. J. Vlassak, William D. Nix, “A New Bulges Test Technique for the Determination of Young’s Modulus and Poisson’s Ratio of Thin Films.”, J.Mater.Res.,Vol.7, 12 (1992) 3242

43. V. M. Paviot, J. J. Vlassak, William D. Nix, ”Measuring the Mechanical Properties of Thin Metal Films by Means of Bulge Testing of Micromachined Windows.”, Mat. Res. Soc. Symp. Proc., 356 (1995) 579

44. Xing Zhang, Costas P. Grigoropoulos, “Thermal Conductivity and Diffusivity of Free-Standing Silicon Nitride Thin Films.”, Rev. Sci. Instrum.66(2), February (1995) 1115

45.E. Obermeier, “Mechanical and Thermophysical Properties of Thin Film Materials for MEMS: Technique and Devices.”, Mat. Res. Soc. Symp. Proc., 444 (1997) 39

46.”Modeling Integrated Sensors/Actuators Functions in Realistic Environments.”, First European Conference on Smart Structure and Materials., EOS/SPIE EUROPTO Series, SPIE 1777(1997) 1

47. William H. Cubberly, Paul M. Unterweiser, David Benjamin, Vicki Knoll, Kathy Nieman, Metals Handbook, 9th ed., American Society for Metals,3 (1980) 272, 645, 670

48. C. R.Tellier, A. J.Tosser, “Size effects in thin films”, Elsevier, 1982, Ch. 1~4

49. S. Timoshenko, S. Woinowsky-Krieger, Theory of plates and shells, McGraw-Hill, 1959, Ch. 1, p. 3

50. W. D. Nix, ‘Mechanical properties of thin films’, Metallugrical Transactions, 20A (1989) 2217

51. J. A. Thornton, “ High rate thick film growth ”, Am. Res. Sci. 7 (1977) 239

52. E. Bonnotte, P. Delobelle, L. Bornier, J. Mater. Res., Vol. 12, 9 (1997) 2234

53. J. Pethica, R. Hutchings, W. C. Oliver, Phil. Mag., A48 (1987) 593

54. J. L. Loubet, J. M. Georges, J. M. Marchesini, G. Meille, J. Tribol, 106 (1985) 43

55. S. Timoshenko, S. Woinowsky-Krieger, Theory of plates and shells, McGraw-Hill, 1959, Ch. 1, p. 3

56. J. W. Beams, “Structure and properties of thin films”, John Wiely and Sons, New York, 1959, p.183

57. S. Tamulevicius, “Stress and strain in the vacuum deposited thin films”, Vacuum, Vol.51, 2 (1998) 127

58. O. Tabata, K. Kawahata, S. Sugiyama, I. Igarashi,”Mechanical properties of thin films using load-deflection of composite rectangular membranes”, Sensors and Actuators 20 (1989) 135

59. Milton Ohring, The Materials Science of Thin Films, Academic Press, London, 1992, Ch. 9, p. 414

60. F. Spaepen, “interfaces and stresses in thin films”, Acta mater. 48 (2000) 31

61. M. Kitabatake, P. Fons, J. E. Greene, “Molecular dynamics simulations of low-energy particle bombarment effects during vapor-phase crystal growth”, J. Vac. Sci. Technol. ,A 8, 5 (1990) 3726

62. B. Window, F. Sharpies, N. Savvides, “Plastic flow in ion-assited deposition of refractory metals”, J. Vac. Sci. Technol. ,A 6, 4 (1988) 2333

63. J. A. Thornton, “High rate thick film growth”, Am. Res. Sci. 7 (1977) 239

64. Kotake S., Molecular Mechanical Engineering (review). JSME Int. J., Series B 38 (1995) 1-7

65. Pan C. S. and Hsu W., "A Microstructure for in-situ Determination of Residual Strain", IEEE/ASME J. Microelectromechanical Systems, Vol. 8, 2 (1999) 200.

66. Pan C. S., "A Simple Method for in situ Determination of Linear Thermal Expansion Coefficients of Thin Films", The Symposium on Instrumentation, Measurements, and Sensors at the 2000 ASME International Mechanical Engineering Congress and Exposition, November 5-10, 2000, Orlando, Florida, USA

67. Pan C. S., "A Simple Microstructure Serves as a Material Characterization Structure", Internal Symposium on Smart structures and Microsystems, Oct. 19-21, 2000, in the Jockey Club, Hong Kong.

68. Fedder G K and Howe R T, "Thermal Assembly of Polysilicon Microstructures", Proc. Micro Electro Mechanical Systems (Nara), (1991) 63-68

69. Wen-Hwa Chut, Mehran Mehregany and Robert L Mullen, "Analysis of tip deflection and force of a bimetallic cantilever microactuator" J. Micromech Microeng. 3 (1993) 4-7

70. 歐憲璋，"熱動式微致動器尺寸最佳化之探討"，成功大學工程科學系碩士論文

71. Baltes H., "CMOS vacuum sensors and other application of CMOS thermopiles", 7th Int. Conf. Solid-State Sensors and Actuators Transducers' 93), Yokohama, Japan, June 7-10, (1993)736-741.

72. Lenggenhager R. and Baltes H., "Improved thermoelectric infared sensor using double poly CMOS technology", 7th Int. Conf. Solid-State Sensors and Actuators (Transducers' 93), Yokohama, Japan, June 7-10, (1993) 1008-1011.

73. S. A. Campbell, H. J. Lewerenz, “Semiconductor micromachining” Vol. 2, John Wiely and Sons, New York, 1998, Chap. 1

74. Milton Ohring, The Materials Science of Thin Films, Academic Press, London, 1992, Ch. 3, p. 111, 113

75. Milton Ohring, The Materials Science of Thin Films, Academic Press, London, 1992, Ch.3, p. 112

76. C. R.Tellier, A. J.Tosser, “Size effects in thin films”, Elsevier, 1982, p103

77. C. R.Tellier, A. J.Tosser, “Size effects in thin films”, Elsevier, 1982, p.11

78. Milton Ohring, The Materials Science of Thin Films, Academic Press, London, 1992, Ch. 9, p. 456

79. H. Windischmann,”Intrinsic stress in sputtered thin films” J. Vac. Sci. Technol. A. 9 (1991) 2431

80. W. D. Nix, B. M. Clemens, “Crystallite coalescence: a mechanism for intrinsic tensile stresses in thin films”, J. Mater. Res. 14 (1999) 3467

81. M. Itoh, M. Hori, S. Nadahara, “The original of stress in sputter-deposited tungsten films for x-ray masks”, J. Vac. Sci. Technol. B9 (1991) 149

82. W. D. Nix, Mechanical properties of thin films, Metallurgical Transactions A, 20 A (1989) 2217

83. M. K. Small, J. J. Vlassak, S. F. Powell, B. J. Daniels, W.D. Nix, “Accuracy and reliability of bulge test experiments”, Mat. Res. Soc. Symp. Proc. 308 (1993) 159