Etch rate and surface roughness of deep narrow U-grooves in (110)-oriented silicon

Long U-shaped grooves that have been anisotropically etched into (110)-oriented silicon with KOH are required for many microsensors and actuators like for microcoolers, force sensors, separating trenches, printheads, etc. Specifications for the etched structures (such as minimum roughness, steep walls or high etch uniformity) require different etch parameters. The etch rates, etch-rate ratios and roughness of the (110) planes are investigated as a function of the KOH temperature and concentration. An important influence on the etch process, especially during the etch of narrow grooves, is also exerted by the (311) planes observed at KOH concentrations above 30%.