Method for controlling an N-type dopant concentration depth profile in bipolar transistor epitaxial layers

US6346452B1 · kind B1 · utility

Assignee

• NATIONAL SEMICONDUCTOR CORPORATION · US

Inventors

• Abul Ehsanul Kabir · Sunnyvale, US
• Rashid Bashir · Champaign, US

Key dates

• Filing date: May 3, 1999
• Grant date: Feb 12, 2002
• Expiry date: May 3, 2019

Classification

• Technology area (CPC H): Electricity
• CPC primary: H10D62/60

Abstract

Process for the formation of epitaxial layers with controlled n-type dopant concentration depth profiles for use in NPN bipolar transistors. The process includes first providing a semiconductor substrate (e.g. a [100]-oriented silicon wafer substrate) with an n-type collector precursor region formed on its surface, followed by forming an n-type (e.g. phosphorous or arsenic) in-situ doped epitaxial layer of a thickness t1 on the n-type collector precursor region. Next, an undoped epitaxial layer of a thickness t2 is formed on the n-type in-situ doped epitaxial layer. A p-type (e.g. boron) in-situ doped epitaxial base layer is subsequently formed on the undoped epitaxial layer. The process can also include the sequential formation of an undoped Si1−xGex epitaxial layer and a p-type in-situ doped Si1−xGex epitaxial layer between the undoped epitaxial layer and the p-type in-situ doped epitaxial base layer. Accumulation of the n-type dopant concentration in p-type epitaxial layers (such as the p-type in-situ doped epitaxial base layer or the p-type in-situ doped Si1−xGex epitaxial layer) that are formed subsequent to a non-p-type epitaxial layer (such as the undoped e…