Characterization of Multi-fin Quantum Well Structures using Photo-conductance Decay Technique

Open Access
Author:
Vakil, Apoorva Babu
Graduate Program:
Electrical Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
July 12, 2012
Committee Members:
  • Jerzy Ruzyllo, Thesis Advisor
Keywords:
  • Electrical Characterization
  • Photoconductance Decay
  • FinFET
  • Fin sidewalls
Abstract:
The era of traditional ‘Moore’s Law’ scaling of transistors encountered a roadblock with problems like short channel effects and sub-threshold leakage current increasingly plaguing the MOS devices. As a result the industry began to show a shift towards non-conventional approaches such as three-dimensional (non planar) device architecture. Electrical characterization techniques are used for probing electronic properties of the material systems, which serve as means of predicting their behavior in the final device. The conventional electrical characterization techniques could no longer be successfully and reliably used to characterize the ‘Fin’ structures with added complexities like vertical sidewall orientation and extremely confined geometry. This work suggests adapting and evaluating the Photo-Conductance Decay (PCD) minority carrier lifetime measurement technique for specific needs of fin-shaped semiconductor material systems. In this work, multi-fin non-gated III-V test structures were used, wherein each fin is comprised of heterogeneously integrated multi-layer MBE grown In0.7Ga0.3As quantum well structures. Fin width was varied across the sample, thus leading to progressively more and more number of fins within the same area. The PCD tool, built around a standard probe station, is a simple tool which allowed calculation of minority carrier lifetime from the extracted PCD curves. The results obtained confirmed the viability of the suggested PCD approach for multi-fin 3D structure characterization. The PCD curves depicted the fin surface and sidewall quality. Poorly formed fins gave a lower minority carrier lifetime, whereas lifetime shown by good quality fins was significantly higher. This work is also concerned with the effect of several surface passivation techniques on the minority carrier lifetime of III-V material systems.