Photoexcited Anisotropic Etching of Single-Crystalline Silicon

Anisotropic etching reaction of single-crystalline silicon (Si) was studied under illumination by a high-pressure Hg lamp employing Cl2. Etch rates of n-type Si decreased in the order of {100}, {110} and {111} planes. As the resistivity deceased and the temperature increased, the etch rate increased. With the resistivity of 0.015 Ωcm and at 200°C, {100} and {110} planes show considerably high etch rates, while the etch rate of the {111} plane was extremely low. By utilizing the specific etch rate difference and retaining an Si oxide pattern in the same direction as , a microdiaphragm with an oxide lever was fabricated.