Self-aligned mask formed utilizing differential oxidation rates of materials

US6844225B2 · kind B2 · utility

Assignee

• International Business Machines Corporation · US

Inventors

• Huajie Chen · Danbury, US
• Kathryn T. Schonenberg · Wappingers Falls, US
• Gregory G. Freeman · Hopewell Junction, US
• Andreas D. Stricker · South Burlington, US
• Jae-Sung Rieh · Seoul, KR

Key dates

• Filing date: Jan 15, 2003
• Grant date: Jan 18, 2005
• Expiry date: Jan 15, 2023

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y10S438/911
• WIPO field: Semiconductors
• WIPO sector: Electrical engineering

Abstract

A self-aligned oxide mask is formed utilizing differential oxidation rates of different materials. The self-aligned oxide mask is formed on a CVD grown base NPN base layer which compromises single crystal Si (or Si/SiGe) at active area and polycrystal Si (or Si/SiGe) on the field. The self-aligned mask is fabricated by taking advantage of the fact that poly Si (or Si/SiGe) oxidizes faster than single crystal Si (or Si/SiGe). An oxide film is formed over both the poly Si (or Si/siGe) and the single crystal Si (or Si/siGe) by using an thermal oxidation process to form a thick oxidation layer over the poly Si (or Si/siGe) and a thin oxidation layer over the single crystal Si (or Si/siGe), followed by a controlled oxide etch to remove the thin oxidation layer over the single crystal Si (or Si/siGe) while leaving the self-aligned oxide mask layer over the poly Si (or Si/siGe). A raised extrinsic base is then formed following the self-aligned mask formation. This self-aligned oxide mask blocks B diffusion from the raised extrinsic base to the corner of collector.