Methods for forming a gate dielectric film of a semiconductor device

Abstract

There is provided a method for forming a gate dielectric film of a semiconductor device, which can minimize the nitrogen induced defects inside the gate dielectric film to enhance the time dependent dielectric breakdown (TDDB) characteristic of the gate dielectric film. In the present invention, a silicon substrate is annealed with N2O (or NO) gas under a low pressure of 10˜100 Torrs to form an oxynitride film on the silicon substrate, or a previously formed thermal oxide film is annealed with the same gas under the low pressure to be nitrified. The annealing under such a low pressure according to the invention allows the number of nitrogens existing inside the oxide film to be relatively fewer than the annealing under the normal pressure according to the method of the prior art, and does the nitrogens to be mainly piled-up at the boundary surface of Si/SiO2. Accordingly, the present invention can allow the nitrogens to bind to the silicon dangling bonds, the strained Si—O bonds and the likes at the Si/SiO2 boundary surface, and suppress the nitrogen induced defects such as bridging nitrogen centers derived from the excess nitrogens inside the oxide film.

Dependencies are inferred from the claim text.