Rectangular Substrate Interconnects for High-Resolution RF Packaging

The fabrication process is segmented into distinct stages: forming mandrels with cylindrical cross-sections, depositing conformal layers, and performing anisotropic etching. Each stage performs a specific function that contributes to the final rectangular cross-section, breaking down the complex transformation into manageable steps that achieve high precision without requiring entirely new fabrication equipment.

Mandrels serve as intermediary structures that are easier to fabricate with cylindrical cross-sections using conventional processes. These mandrels act as templates that guide the subsequent conformal deposition and anisotropic etching steps, ultimately producing the desired rectangular interconnects. The intermediary mandrel structure bridges the gap between conventional fabrication capabilities and advanced interconnect geometries.

The method employs anisotropic etching with directionally selective removal rates, where the etch rate varies significantly with crystal orientation. By controlling the etching parameters and mandrel geometry, the process transforms cylindrical mandrels into rectangular interconnects with precise dimensions. This parameter control enables consistent reproduction of high-resolution features across multiple devices.

The patent replaces direct mechanical shaping methods with a chemical etching process that selectively removes material based on crystallographic orientation. This substitution allows for more precise control of interconnect geometry and reduces mechanical stress that would be introduced by conventional mechanical shaping methods, thereby improving manufacturing precision while maintaining ease of manufacture through established semiconductor processing techniques.