System and method for determining thin-film stress based on deformation measurement and numerical reverse

Abstract

The invention provides a simple, flexible and reliable thin-film stress measuring system and a measuring method. The invention adopts shape-measuring equipment to measure the deformation of a thin-film material caused by thin-film stress, and expresses the deformation as the deflection or the cross-section corner of the thin-film material. The invention adopts a plate structural finite element to discrete the geometric model of a detected object, so as to give all or part of measuring values of the nodal freedom degree of the finite element in a direct measurement or indirect interpolation mode, when data are measured and processed, the influence of external force on deformation measurement is modified. The least-squares fitting condition between the deformation generated by the thin-film stress at the nodes and the deformation given by measurement is established to reversely calculate the thin-film stress by regularization process. In the condition of irregular plane form, uneven thickness of a sample and the thin-film, uncertain parameters of the thin-film material, the invention can be used for identifying anisotropic and non-uniformly distributed thin-film stress.

Description

technical field [0001] The invention pertains to measurement techniques used in the manufacture of integrated circuits and micro-electromechanical systems (MEMS), which are used to measure thin-film stress in thin-film materials. Background technique [0002] Thin film materials are widely used in the manufacture of integrated circuits and microelectromechanical systems (MEMS). After chemical deposition (CVD) and physical deposition (PVD) techniques are used to form thin film materials with specific properties and functions on the surface of the substrate, the thin film materials can be processed into integrated circuits and microchips by using micromachining processes such as masks, photolithography, and corrosion. structure. Non-negligible stress inevitably occurs in the thin film material due to the crystal defects generated during the film formation process and the difference between the thermal expansion coefficients of the thin film material and the base material. Th...

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Problems solved by technology

Although this method avoids the problem of using non-coordinated strains, it still has the following obvious defects: (1) It is generally impossible to measure the kinematic variables of all nodes. Except for the nodes on the boundary, the internal nodes are not measurable. It can only be obtained by interpolation; (2) It is difficult to ensure sufficient accuracy in the measurement of degrees of freedom such as rotation angles; (3) The coordination condition between the deformation of the substrate and the film is not considered; (4) The calculation needs to use the material parameters of the film; and (5) The influence of correcting external forces (such as self-weight) on the measured deformation is not considered

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