Process for semiconductor device fabrication

Abstract

The present invention is directed to a process for fabricating a semiconductor integrated circuit device, and specifically, a process for cleaning a silicon substrate before gate silicon dioxide is formed on the silicon substrate. The gate silicon dioxide is used to form transistor gates. The process of the present invention provides a silicon/silicon dioxide interface and the bulk silicon dioxide with advantageous electrical properties. In the present process, the silicon substrate is first subjected to a stream of hydrofluoric acid (HF) vapor. The vapor HF stream is a mixture of anhydrous HF, methanol, and nitrogen. Following this, the substrate is subjected to gaseous chlorine that has been irradiated with broad band UV radiation. After the substrate has been cleaned according to the present process, a layer of silicon dioxide is grown thereon using conventional techniques such as rapid thermal oxidation (RTO). It is advantageous if the cleaned silicon surface is kept under high vacuum or in an inert gas environment before the oxide growth is commenced. In the context of the present process, it is advantageous if the substrate is maintained in an essentially oxygen-free atmosphere from the time the HF vapor step is started until the growth of silicon dioxide is commenced. After the oxide is grown thereon, device structures are formed on the silicon substrates using conventional processing techniques.