Abstract: This paper experimentally studies the effects of the conductivity of a silicon wafer and the gap height between silicon structures and glass substrate on the footing effect for silicon on glass (SOG) structures in the deep reactive ion etching (DRIE) process.Experiments with gap heights of 5,20,and 50μm were carried out for performance comparison of the footing effect.Also,two kinds of silicon wafers with resistivity of 2~4 and 0.01~0.03Ω·cm were used for the exploration.The results show that structures with resistivity of 0.01~0.03Ω·cm have better topography than those with resistivity of 2~4Ω·cm;and structures with 50μm-high gaps between silicon structures and glass substrate suffer somewhat less of a footing effect than those with 20μm-high gaps,and much less than those with 5μm-high gaps.Our theoretical analysis indicates that either the higher conductivity of the silicon wafer or a larger gap height between silicon structures and glass substrate can suppress footing effects.The results can contribute to the choice of silicon type and optimum design for many microsensors.

Key words: footing effect, silicon on glass, deep reactive ion etching.