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OXIDATION OF SILICON-GERMANIUM ALLOY FILMS

IP.com Disclosure Number: IPCOM000006520D
Original Publication Date: 1992-Aug-01
Included in the Prior Art Database: 2002-Jan-11
Document File: 1 page(s) / 65K

Publishing Venue

Motorola

Related People

Gordon Tam: AUTHOR [+4]

Abstract

Silicon-germanium (SiGe) heterojunction bipolar transistors (HBTs) have recently demonstrated their high- speed capability over conventional bipolar-devices. Besides the low-temperature processing constraints required for maintaining the strained properties of SiGe films, oxidation remains the major difference between SiGe and Si processing. Conventional wet (or dry) ther- mal oxidation and rapid thermal oxidation of the SiGe films have resulted in oxide layers with Ge piling up at the oxide-silicon interface. This piling up of Ge at the interface can produce leakage paths, resulting in poor isolation between electrodes or devices. University research has shown high pressure oxidation at 680 atm. (and 550°C in dry 02) to be effective in reducing Ge pile up at oxide-silicon interfaces when oxidizing single crys- tal SiGe iilms. Unfortunately, a high pressure oxidation system operating at 680 at*. is not commercially available.

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MOTOROLA INC. Technical Developments Volume 16 August 1992

OXIDATION OF SILICON-GERMANIUM ALLOY FILMS

by Gordon Tam, Richard Gregory, Lynnita Knock and Nirmal D. Theodore

  Silicon-germanium (SiGe) heterojunction bipolar transistors (HBTs) have recently demonstrated their high- speed capability over conventional bipolar-devices. Besides the low-temperature processing constraints required for maintaining the strained properties of SiGe films, oxidation remains the major difference between SiGe and Si processing. Conventional wet (or dry) ther- mal oxidation and rapid thermal oxidation of the SiGe films have resulted in oxide layers with Ge piling up at the oxide-silicon interface. This piling up of Ge at the interface can produce leakage paths, resulting in poor isolation between electrodes or devices. University research has shown high pressure oxidation at 680 atm. (and 550°C in dry 02) to be effective in reducing Ge pile up at oxide-silicon interfaces when oxidizing single crys- tal SiGe iilms. Unfortunately, a high pressure oxidation system operating at 680 at*. is not commercially available.

  We have demonstrated that high pressure oxidation at 25 atm. and 750°C in a wet 0~ environment is suffi- cient to prevent piling up of Ge at oxide-silicon inter- faces for both single crystal and polycrystalline SiGe films. FLBS shows that Ge resides within the oxide layer after high-pressure oxidation. Cross-sectional TEM micro- graphs indicate that .the majority of the Ge...