Method for Forming an Emitter/Collector of a Silicon On Insulator Lateral Bipolar Transistor by Lateral Epitaxial Growth
Publication Date: 2014-Mar-12
The IP.com Prior Art Database
A method is disclosed for forming an emitter/collector of a Silicon On Insulator (SOI) lateral bipolar transistor by lateral epitaxial growth.
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Method for Forming an Emitter /
/Collector of a Silicon On Insulator Lateral Bipolar
Collector of a Silicon On Insulator Lateral Bipolar
Transistor by Lateral Epitaxial Growth
In Silicon On Insulator (SOI) lateral bipolar technology, it is desired to have a heterojunction device structure, with larger energy gap semiconductor for the emitter.
An example is the Si-emitter SiGe-base Heterojunction Bipolar Transistor (HBT) described in US 8,288,758.
To form a wide-gap emitter, the conventional method is to provide a Si seed layer underneath the base semiconductor material in the emitter region so that the Si emitter can grow vertically from the Si seed layer. This is described in US 8,420,493.
In practice, it is a challenge to control the Si seed layer thickness, due to process variation, over etching during etching of the base semiconductor material , etc. Furthermore, with a Si seed layer, there is a parasitic Si-emitter Si-base bipolar transistor formed from the Si seed layer.
Disclosed is a method for forming an emitter /collector of a SOI lateral bipolar transistor by lateral epitaxial growth. The use of lateral epitaxial growth in lieu of a vertical epitaxial growth helps in forming a wide-gap emitter HBT on SOI without the need for a seed layer for epitaxial growth of the emitter and collector. The resulting device structure accordingly has no parasitic bipolar device due to the seed layer .
The following describes an embodiment of the method for fabricating a SOI lateral npn Si-emitter SiGe-base transistor. The method can be readily extended to a SOI lateral pnp Si-emitter SiGe-base transistor. Further, a similar method can be applied for SOI lateral Ge-base transistor with one of Si-emitter and SiGe-emitter.
In accordance with the embodiment, the method starts with a p type SiGe on insulat...