A test structure and measurement method for the stress gradient of a mems microbeam with a detection hole

Abstract

The invention discloses a structure for testing the stress gradient of an MEMS micro beam with a detection hole, and a measurement method. The structure comprises a substrate, two long anchor regions, and six tested cantilever beams with detection holes. The two long anchor regions are fixed on the upper surface of the substrate. One end of each tested cantilever beam is fixed on a side surface of the corresponding long anchor region, and the other end of each tested cantilever beam is provided with a square through hole in an etching manner, wherein the square through holes serve as the detection holes, and side wall of the detection holes are perpendicular to the surface. Each three tested cantilever beams serve as a group, and each group of tested cantilever beams are fixed in the corresponding long anchor region. The suspension ends of the two groups of tested cantilever beams are opposite to each other, and are oppositely arranged in a completely symmetric manner. When the tested cantilever beams are bent upwards or downwards because of the stress gradient, the side walls of the detection holes will be inclined accordingly. The mechanism can judge the bending condition of the tested cantilever beams according to the observed projection area of the front or rear side walls on a horizontal plane. The method can reduce the requirements for observation equipment, and is visual and convenient.

Description

technical field [0001] The invention relates to the technical field of stress gradient testing in a MEMS cantilever structure manufactured by MEMS micromachining technology in microelectromechanical systems (hereinafter referred to as MEMS). Specifically, it relates to a test structure and a measurement method for the stress gradient of a MEMS microbeam with a detection hole. Background technique [0002] The stress in MEMS (Micro-Electro-Mechanical Systems) structure mainly comes from thermal stress, internal stress and external stress. The stress caused by the difference in thermal expansion coefficient of each thin film layer is thermal stress; the stress generated by the microstructure changes such as lattice mismatch, impurity atoms, grain boundary relaxation, etc. is internal stress (also called intrinsic stress); When the surface of the material is not very dense, some polar molecules in the environment will be adsorbed on the gaps, and the stress generated by the in...

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Problems solved by technology

Therefore, during the MEMS process, residual stress will inevitably be generated. When the stress distribution along the thickness direction of the material is non-uniform, that is, there is a stress gradient, the cantilever beam structure or the fixed-supported beam structure fixed at both ends, after the structure is released ( corrode the support sacrificial layer under the beam, so that the beam is suspended), there will be out-of-plane bending or buckling, which directly affects the performance of the device

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