This work investigates the effects of post-fabrication applied mechanical tensile
strain on Silicon (Si) Bipolar Junction Transistor (BJT) and Silicon-Germanium (SiGe)
Heterojunction Bipolar Transistor (HBT) devices. Applied strain effects on MOSFET transistors
are being heavily explored, both in academia and industry, as a possible alternative
to dimensional scaling. This thesis focuses on how strain affects Si BJT and SiGe HBTs,
where tensile strain is applied after the Integrated Circuit (IC) fabrication has been completed, using a unique mechanical method. The consequence of both biaxial and uniaxial
strain application has been examined in this work.
Chapter I gives a short introduction to the scope of this work, the motivation for conducting
this research and the contributions of this experiment.
Chapter II entails a brief discussion on Si bipolar and SiGe heterojunction bipolar device
physics, which are key to the understanding of strain induced effects.
Chapter III provides a thorough summary of the current state of research regarding
applied strain, also known as Strain Engineering. It covers different types, orientations,
and application techniques of strain.
Chapter IV, highlights the details of this experiment, and also presents the measured
results. It is observed that for this particular method of biaxial tensile strain application,
the collector current (IC) and current gain degrades for both Si BJT and SiGe HBT.
Base current (IB) decreases in Si BJT, though it increases for SiGe HBT after strain. Little
or no change is noticed in the dynamic or ac small-signal characteristics like unity-gain
cutoff frequency (fT) and base resistance (rBB) after strain. Uniaxially strained SiGe HBT
samples showed similar results as the biaxial strain. This chapter also attempts to explain
the origin of these strain induced changes.
Chapter V, summarizes the finding of this experiment, and concludes the thesis with
some future directions for this research.
| Identifer | oai:union.ndltd.org:GATECH/oai:smartech.gatech.edu:1853/7192 |
| Date | 18 July 2005 |
| Creators | Nayeem, Mustayeen B. |
| Publisher | Georgia Institute of Technology |
| Source Sets | Georgia Tech Electronic Thesis and Dissertation Archive |
| Language | en_US |
| Detected Language | English |
| Type | Thesis |
| Format | 12539249 bytes, application/pdf |
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