Silicon trench etch in a hex reactor.

The fabrication of trench structures in single crystal silicon substrates for dielectric isolation or buried capacitors is readily achievable in a hexagonally configured, low pressure plasma etch system using chlorine chemistry. A number of process concerns are discussed: prevention of "grass", sloped sidewalls for proper trench filling, process etch uniformity and construction and some electrical results of trench capacitors. The transition to load-locked etch systems has allowed chemistry additions that are beneficial for trench etch rate and profile control. Laser interferometry has been successfully used to monitor etch rate, control end point and detect film interfaces for wafers with 5 per cent exposed silicon.