Method for forming self-aligned t-shaped transistor electrode

摘要

A T-shaped electrode is formed on a semiconductor substrate by first forming a dielectric film on the substrate. A first layer of photoresist is applied on the upper surface of the dielectric film, and a second layer of photoresist is applied over the first layer of photoresist. The first and second layers of photoresist have different optical properties, requiring different wavelengths of ultraviolet for exposure before developing. Portions of the first and second photoresist layers and the dielectric film are selectively removed by photolithographic techniques with one masking step for forming an opening to the substrate. The first and second photoresist layers adjacent to the opening are ion etched to expose the upper surface of the dielectric film adjacent to the opening. A portion of the first photoresist layer adjacent to the opening is removed to undercut the second photoresist layer. Metal is deposited in the opening and on the exposed upper surface of the dielectric film to form a T-shaped electrode. The first and second photoresist layers are then removed, thereby also removing metal deposited on top of the second layer of photoresist.