Elastic Modulus
Physical constant representing the stiffness of a material that remains identical regardless of the direction of the applied load defines the value. Isotropic youngs modulus simplifies the mechanical modeling of materials like glass or certain polycrystalline metals. Parameter relates the stress on a body to the resulting strain.
Material Selection
Choosing a material with a uniform modulus ensures that the sensor responds predictably to forces from any angle. In micro-electronics, silicon is actually anisotropic, but some thin-film coatings are treated as isotropic for the purpose of simulation. Assumption reduces the computational complexity of the design process.
Stress Distribution
Even application of pressure across a diaphragm depends on the consistency of the underlying material properties. If the modulus varies, the structure might warp or buckle in an unpredictable manner. Maintaining a uniform thickness and composition of the deposited layers is necessary for achieving a stable output.
Temperature Dependency
Modulus of elasticity typically decreases as the temperature rises, making the structure more flexible. This change must be compensated for in the sensor signal processing logic to maintain accuracy across the full operating range. Characterization involves measuring the resonant frequency of a test structure at various temperatures to determine the thermal coefficient of the material.
By understanding this relationship, engineers can design more stable devices for harsh environments. The final calibration step accounts for the remaining variance to ensure the product meets its specification. Verification of the material properties occurs through nano-indentation testing of sample wafers.
