SiC Plasma Etching Profile Control via Two-Step Passivation

The etching process is divided into two distinct steps: a first anisotropic etch step that creates the main trench structure with substantially perpendicular sidewalls and a flat bottom surface, followed by a second plasma etch step that selectively rounds the corners. This segmentation allows each step to be optimized for its specific function, achieving both high productivity and precise profile control without micro-trenching

The first etch step performs the preliminary action of creating the bulk trench structure with the desired depth and width before the second step addresses the corner rounding. By preparing the substrate with a flat-bottomed trench first, the subsequent corner rounding process can focus solely on modifying the peripheral regions without affecting the overall trench geometry, thereby maintaining fabrication efficiency while improving profile precision

The method merges the trench formation and corner rounding operations into a single integrated plasma etching process with two controlled steps, both performed in the same reactor using the same mask structure. This merging eliminates the need for separate processing steps that would require additional equipment, mask changes, and chamber transitions, thereby maintaining high fabrication throughput while achieving precise profile control through the coordinated action of the two etch steps

The single plasma etching system performs multiple functions: it creates the main trench structure in the first step and rounds the corners in the second step, all while using the same mask layer and process chamber. This multi-functionality reduces equipment requirements and process complexity compared to using multiple specialized processing steps, thereby improving productivity without sacrificing manufacturing precision

The process uses dynamic control of plasma parameters during the two etching steps to achieve different outcomes from the same basic process. By adjusting power, pressure, and gas flow between the first and second steps, the process transitions from creating straight-walled trenches to rounding corners, all within a single etching system. This dynamic parameter adjustment adds control capability without requiring additional physical process steps or equipment

The method relies on changing plasma process parameters (such as power, pressure, and gas composition) between the first and second etching steps to achieve different etching characteristics. The first step uses parameters optimized for anisotropic etching with perpendicular sidewalls, while the second step uses modified parameters that promote corner rounding. These parameter changes are implemented through software control of the same etching equipment, avoiding the need for additional physical process steps