Mechanism and technology of laser selective removal of multilayer materials

Multilayer material composed of two or more layers of heterogeneous materials, and it has been widely applied in integrated circuits, wearable devices due to their compact structure and high integration density. However, the selective nondestructive removal of one or more layers in multilayer materials is a long-pending challenge. In this paper, an innovative method for laser selective removal of multilayer materials based on induced spectral coaxial detection was proposed. The technologies of laser scanning processing and coaxial spectrum monitoring were integrated. During the layer by layer removal, the two-dimension (2D) and three-dimension (3D) element mapping were reconstructed synchronously in situ by continuous spectral analysis. The mechanism of interface sensing and the principle of laser selective removal of multilayer materials were investigated. Moreover, the selective removal of copper layer on the surface of FR-4 copper clad laminate (CCL) was achieved with a directional removal rate up to 99.13 %, and ablating damage was only 0.190 mu m. The method shows great material applicability, interface perception sensitivity and high-precision micro/nano removal capability. Since different materials have their own special spectral lines, this method is not only applicable to selective removal of FR-4 CCL, it also provides an effective route for selectively removing other multilayer materials, without the limitations of material type and number of layers, which provides a valuable guideline for solving the common problem of directional removal of multilayer materials.

Automated summary

An innovative method for laser selective removal of multilayer materials based on induced spectral coaxial detection was proposed in this paper. By integrating laser scanning processing and coaxial spectrum monitoring technologies, two-dimension (2D) and three-dimension (3D) element mapping were reconstructed synchronously in situ during the layer by layer removal. The method achieved a directional removal rate up to 99.13% and minimal ablating damage, providing a valuable guideline for selectively removing other multilayer materials.