Tham khảo tài liệu 'micro electro mechanical system design - james j. allen part 5', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | MEMS Technologies 101 b Archimede Spirals with inner and outer anchors FIGURE Residual stress gradient test structures. stress through the film thickness Equation . The simplest test structure to assess the residual stress gradient is an array of cantilever beams Figure . The out-of-plane deflection due to the internal bending moment can be simply calculated 49 however the quantitative measurement of the out-of-plane deflection requires an SEM or interferometer. Figure shows another test structure used to measure residual stress gradients the Archimedes spiral 50 . The spiral will expand or contract upon release from the substrate three response variables endpoint height endpoint rotation and lateral contraction may be related to the residual stress gradient. This gradient can be estimated from just one of the variables two of the variables can be simply obtained with an optical microscope which is advantageous. However the Archimedes spiral may need to be large to obtain the required sensitivity. t M 2 a y ytfy 2 Young s Modulus Young s modulus E Section which is the proportionality between stress a and strain and the essential parameter for calculation of the stiffness of structures is necessary for design. This modulus may be obtained by directly 2005 by Taylor Francis Group LLC 102 Micro Electro Mechanical System Design Electrostatic interdigitated comb drive Anchor Double folded spring WllllllllWllllllllIIIIHllllll FIGURE Electrostatic resonator test structure. testing the thin-film material using specialized devices such as a nanoindenter which plunges a diamond tip into the material and measures the deformation. Alternatively a lateral electrostatic resonator Figure may be used to extract the value of Young s modulus. The lateral resonator moves parallel to the substrate and thus minimizes damping effects and allows observation with an optical microscope. The resonator structure is driven by opposed .
