United Microelectronics Corp.

Yann-Pyng Wu

Yueh-Feng Ho

Gow-Wei Sun

First of all, a semiconductor substrate is provided, the semiconductor substrate has a dielectric layer thereon. Then a photoresist layer is formed and defined on the dielectric layer. Next, an etching process is performed by the photoresist layer as an etched mask to form a trench in the dielectric layer, wherein the etchant of the etching process comprises a mixing gas with a C F gas or a CH F gas, such as C F /CH F /Ar/O or C F /CH F /Ar/O /CF or C F /CH F /Ar/O /C F , accordingly, the etching capability of the etchant and the etching selectivity between the dielectric layer and the photoresist layer can be raised. Finally, the photoresist layer is removed to form the contact window or the via hole with high accurate critical dimension.

Etching process for forming the trench with high aspect ratio

A method of forming floating gates for flash memory is disclosed to improve contact properties with erase gates. The method includes formation of a tunnel oxide layer, a polysilicon layer and an interpoly insulating layer. These layers are patterned in two dry etching steps to complete floating gate definition. In the first etching step, the interpoly insulating layer is etched open in an oxide chamber to form a taper opening. The taper opening is further deepened in the second etching step, in which the polysilicon layer and the tunnel oxide layer are etched open in sequence in a poly chamber. A contact with smooth, vertical surface profile is thus formed in the second etching step. The two-step dry etching procedure is found to provide good contact profile for the floating gate to facilitate subsequent oxide deposition and contact filling. The proposed etching procedure also makes substantial operation reduction for floating gate formation and thus advantageously costs down for flash memory production.

Growing community of inventors

Miao-Li, Taiwan

Yann-Pyng Wu