Laser Processing of 2-D and 3-D Structures for Tunable Embedded Capacitors

Abstract

Material formulation, structuring, and modification are key to increasing the unit volume complexity and density of next generation electronic packaging products. Laser processing is finding an increasing number of applications in the fabrication of these advanced microelectronic devices. This is due, in part, to the ability to achieve highly localized treatment of materials with a spatial resolution of tens of microns. In addition, the process is data-driven, that is, patterns can be generated without the need for masking materials. In the present investigation, a variety of structures have been generated in polymer nanocomposites, nanoparticle films, and sol-gel thin films using a computer-controlled laser system. Specifically, micromachining technology has been used to produce both variable-thickness and discrete capacitors from a single sheet (layer) of capacitor material, such that both types of structures can be integrated into the same layer. In addition, the laser micromachining technology has been extended to design and develop new vertical multilayer embedded capacitors for high speed applications. High speed packages require thick dielectrics. Calculations show that multilayer vertical capacitors can be better than thick capacitors formed from a single layer. In general, multilayer embedded capacitors are fabricated by repeated lamination of resin-coated copper, or pre-preg with a capacitor core. This is a time consuming, lengthy process. As an alternative, we have deposited a single, thick capacitance layer, and subsequent laser micromachining has been used to form multiple parallel channels of a controlled depth. Metal deposition in the channels results in a multilayer embedded capacitor structure. Lasers micromaching can also provide various complex patterns such as 3-D spiral channels within a dielectric or magnetically active nanocomposite, subsequently filled with conducting materials to form inductors. This technique can be used to prepare inductors and capacitors in the same layer of nanocomposite material. Hence, the technique can be used to generate multi-functional structures for tunable device applications.