Method of surface treatment on the improvement of electrical properties for doped silicon oxides (SiO2) films

US6689645B2 · kind B2 · utility

Assignee

• National Science Council · TW

Inventors

• Mau-Phon Houng · Tainan, TW
• Yeong-Her Wang · Tainan, TW
• Wai-Jyh Chang · Tainan, TW

Key dates

• Filing date: May 10, 2001
• Grant date: Feb 10, 2004
• Expiry date: Mar 24, 2022

Classification

• Technology area (CPC H): Electricity
• CPC primary: H01L21/02238
• WIPO field: Semiconductors
• WIPO sector: Electrical engineering

Abstract

In the fabrication of gate oxides in IC process, a suitable cleaning/etching process is required to remove the native oxides and reduce surface microroughness in addition to standard RCA cleaning. For ultrathin oxide thickness (<10 nm), it is an important issue to have a native-oxide-free and H-passivated silicon (Si) surface to ensure high breakdown field, high charge-to-breakdown, and low leakage current. According to these concepts, we propose an invention with a simple two-step hydrogen fluoride (HF) etching process to improve the electrical properties of liquid-phase deposited fluorinated silicon oxides (LPD-SiOF), including effective removal of native oxides, lowering of interface trap density (&#732;1010 eV&#8722;1 cm&#8722;2), reduction of surface microroughness (Ra=0.1 nm), and raising of breakdown field (&#732;9.7 MV/cm). Furthermore, rapid thermal annealing (RTA) is also used to further improve the oxide quality. It is found that 18% increase of breakdown field and 33% reduction of interface trap density can be reached. In addition to the suitability for LPD-silicon oxides (SiO2), this technique is also suitable to other doped oxides. This technology is helpful to obtain…