anisotropic etch

**Anisotropic etch** is a semiconductor etch process in which material is removed much more rapidly in one direction than another. The result is a feature with steep, vertical sidewalls instead of a rounded or undercut profile, which is essential for high-resolution pattern transfer. **The reason this matters is that modern chips need high aspect ratio structures.** Deep trenches, contact holes, and vias require the etch to cut straight down while preserving sidewall integrity. Plasma-based reactive ion etching is a common way to achieve this because directional ion bombardment and sidewall passivation work together to favor vertical removal. **In practice, process conditions matter a lot.** Low pressure, appropriate RF power, and carefully chosen chemistry improve anisotropy, while aspect ratio dependent etching can make very deep features harder to etch uniformly. Engineers often compensate with multi-step recipes or tuning of bias, gas flow, and passivation. | Factor | Effect on etch | |---|---| | Directional ion bombardment | Increases vertical removal | | Sidewall passivation | Reduces lateral attack | | Low pressure | Improves anisotropy | ```svg ``` In short, anisotropic etch is a precision patterning step that creates straight-walled features needed for advanced semiconductor fabrication.