Method for on-line measurement of MEMS membrane stress gradient

Abstract

The invention discloses a method used for online measuring the stress gradient of MEMS film, comprising the steps as follows: a round film with center fixed is prepared on a structure layer film; after the round film is released, the round film generates deformation under the stress gradient inside the round film; the displacement of the edge of the round film in the vertical direction is measured by a non-contact phase-shifting typed Mirau interferometer, thus calculating the curvature radius of the round film; and the stress gradient of the film can be calculated by the young modulus and Poisson ratio of the film and the curvature radius of the round film. The measurement method is characterized in that a centrosymmetric round film with the center fixed is used as a testing structure and a choring area is fixedly clamped closely to an ideal state, thus improving the precision of the model; the non-contact optical interference method is used for measurement, thus not affecting testing structure and having good repeatability; the method is suitable for measuring the stress gradient of conductive material and non-conductive material simultaneously; and furthermore, the measurement method has the advantages of simple and convenient operation, high measurement precision, small chip occupying area and the like.

Description

A Method for On-line Measurement of MEMS Thin Film Stress Gradient technical field The invention relates to a method capable of online measuring the stress gradient of a microelectromechanical system (MEMS) film, and belongs to the technical field of MEMS material parameter measurement. Background technique The application fields of MEMS technology are very broad, and can be used in many fields such as inertial measurement, microfluidics, optics (optical switches, display devices, etc.), pressure measurement, and RF devices. Film deposition is an important process step in the processing of silicon-based MEMS (microelectro-mechanical systems) devices, but due to unfavorable factors such as lattice mismatch, different thermal expansion coefficients between the structural layer and the substrate material, residual stress and thickness will be generated inside the film. The stress gradient in the direction. The stress gradient will cause the deformation of the film and redu...

AI Technical Summary

Problems solved by technology

If you choose a wider cantilever beam as the test structure, the deflection in the width direction will affect the measurement accuracy; if you choose a narrow beam or Archimedes spiral structure, the width cannot be accurately controlled during etching, and the interface along the width direction is not ideal rectangle, these will cause significant error to the measurement accuracy

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