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Etching characteristics of local wet etching of silicon in HF/HNO3 mixtures

Silicon‐on‐insulator (SOI) wafers are promising semiconductor material to realize high speed and low power consumption electric devices. The thickness and deviation of SOI, which are required in the next generation, are 13–15 nm and ± 5%, respectively. However, it is very difficult to achieve those specifications by applying conventional machining, because plastic deformation and brittle fracture in mechanical removal mechanisms inevitably cause subsurface damage such as dislocations, vacancies, or microcracks. Moreover, the accuracy of machining is strongly affected by external disturbances, such as the vibration or thermal deformation of the workpiece and the machine, because of the contact‐removal mechanism. To solve these issues, we had developed numerically controlled local wet etching (NC‐LWE) as a novel deterministic subaperture figuring and finishing method, which utilizes localized chemical reaction between the etchant and the surface of the workpiece. We investigated the etching characteristics of local wet etching of silicon in HF/HNO3 mixtures, and it was found that there was an induction period in the case of scanning the etchant supply nozzle. Copyright © 2008 John Wiley & Sons, Ltd.